
:: 1overf.freq=X	@Since: 2.16
			@Advanced
			The target frequency (Hz) at which the 1/f is measured 
			for logging global 1/f noise statistics. The logged 
			quantity is the ratio of the PSD measured at this 
			frequency to that at the reference frequency. The 
			actual measurement frequency will always be above the
			filter cutoff of 'drifts' filtering.
			@See: '1overf.ref', 'log'

:: 1overf.ref=X		@Since: 2.16
			@Advanced
			The white noise reference frequency used when providing
			1/f noise statistics. If the value exceeds the Nyquist
			frequency of the time-stream, then the Nyquist value
			will be used instead.
			@See: '1overf.freq'

:: 350um		@Instrument: SHARC-2, MAKO-2
			Specify that the 350um filter was used (default). This 
			adjuts conversion factors, tau scaling relations for 
			calculating in-band line-of sight opacitites, and beam 
			sizes (see 'config/sharc2/default.cfg').
			@See: 'jansky', 'tau.<?>', 'beam'.

:: 450um		@Instrument: SHARC-2, SCUBA-2 
			Use if the 450um filter was used to observe with 
			SHARC-2, or to specify 450um imaging with SCUBA-2 and
			MAKO-2.
			@See: '350um' and '850um'

:: 850um		@Instrument: SHARC-2, SCUBA-2, MAKO-2
			Specify that data was taken at 850um with SHARC-2, or
			to reduce the data from the 850um array of SCUBA-2 and
			MAKO-2.
			@See: '350um' and '450um'

:: accel		@Alias -> 'correlated.accel-mag'
			@Advanced
		 	Can be used to enable acceleration response 
			decorrrelation, or to set options for it.
			@See: 'correlated.<?>' for available options.
	
:: aclip=X		@Advanced
			Clip data when the telescope acceleration is above
			X arcsec/s^2. Heavy accelerations can put mechanical
			energy into the detector system, changing the shape of
			the primary, thereby generating bright signals from the 
			varying illumination of the bright atmosphere. Clipping 
			data when there is danger of this happening is a good 
			idea. 
			@See: 'accel' for possible modeling of these signals)

:: alias.<?>		@Advanced
			Use to define convenient shorthands for yourself. 
			Aliases are literal substitutions. Thus:

			    alias.altaz system=horizontal		
			
			can specify 'altaz' to serve as a shorthand for the
			key/value pair 'system=horizontal'. Conditional can also
			be aliased. E.g.:
			
			    alias.final iteration.[last]

			Defines 'final' as a shorthand for 'iteration.[last]'.
			Thus:
			
			    final:smooth=9.0

			is understood as being 

			   iteration.[last] smooth=9.0

			(The colon provides an alternative to a white-space to
			separate the condition from the statement, which is also
			command-line friendly).
			@See: 'altaz', 'final'   

:: altaz		@Alias -> 'system=horizontal' 
			Shorthand for reducing in Alt/Az cordinates.
			@See: 'system' and 'horizontal'.

:: amps			@Alias -> 'correlated.amps'
			@Instrument: LABOCA
			@Advanced
			Decorrelate on amplifier boards, or set options for it.
			@See: 'correlated.<?>' for details on brached options.

:: analyzer=<pos>	@Instrument: PolKa
			@Since: 2.04
			Specify that the analyzer grid position that was used
			for taking the data. Specifying the analyzer is
			important for recovering the polarization information.
			The <pos> must be either 'H' or 'V' corresponding to
			the two positions.
			As of 2011, the analyzer position should be correctly
			recorded in the data file, and therefore automatically
			detected. You can still use 'analyzer' to override the
			recorded setting.

:: analyzer.h.phase=X	@Instrument: PolKa
			@Expert
			@Since: 2.11
			Set the relative phase (degrees) of the total-power 
			modulation for waveplate phase reconstruction with the 
			H analyzer. These phases can be measured using
			'waveplate.tpchar' when the waveplate data is normally
			present.
			@See: 'waveplate.tpchannel', 'waveplate.tpharmonic'
			      'waveplate.tpchar', 'analyzer.v.phase' 	

:: analyzer.v.phase=X	@Instrument: PolKa
			@Expert
			@Since: 2.11
			Set the relative phase (degrees) of the total-power 
			modulation for waveplate phase reconstruction with the 
			V analyzer. These phases can be measured using
			'waveplate.tpchar' when the waveplate data is normally
			present.
			@See: 'waveplate.tpchannel', 'waveplate.tpharmonic'
			      'waveplate.tpchar', 'analyzer.h.phase' 	

:: array		@Alias -> 'correlated.obs-channels'
			@Advanced
			Decorrelate on all the radiation-sensitive channels of
			the instrument, or set options for it.
			@See: 'correlated.<?>' for details on brached options.

:: azimuth		@Alias -> 'correlated.telescope-x'
			@Instrument: GISMO
			@Advanced
			Remove signals, which are correlated to the azymuth
			movement of the telescope (e.g. superconducting detector
			arrays sensitive to Earth's magnetic field.),
			@See: 'correlated.<?>' for details on brached options.

:: beam=X		@Advanced
			Set the instrument beam to X arcseconds.
			@See: 'resolution'

:: beammap		@Deprecated
			@See: 'pixelmap'

:: blacklist[=<list>]	Similar to 'forget', except it will not set options 
			even if they are then specified at a later time. This 
			is useful for altogether removing settings from the 
			configuration.
			@Since: 2.01-4
			Without an argument, the command will produce the list
			of all blacklisted settings on the console.
			@See: 'whitelist', 'forget', 'recall', 'remove', 
			      'replace'

:: blank=X		@Expert
			Skip data from modeling over points that have a source
			flux exceeding the signal-to-noise level X. This may
			be useful in reducing the filtering effect around 
			bright peaks. 
			@See: 'clip'.

:: blind=<list>		@Expert
			Specify a list of blind pixels. Use data indeces (e.g.
			backend indeces for APEX) and ranges, in a comma-
			separated form. E.g.:

			   blind 46,70-72,84

			Blind channels may be used by some instruments to
			estimate instrumental signals, such as temperature
			fluctuations (LABOCA). Channels are normally numbered
			from 1 (i.e. not C-style!)
			@See: 'flag'.

:: block=NX,NY		@Instrument: SHARC-2, SCUBA-2
			@Expert
			Specify a correlated block size for higher order 
			sky-noise removal, as two integer pixel numbers (rows 
			and columns) separated by a comma or 'x'. E.g.:

			   block=4x6

			will correlated.signals on blocks that are 4 columns 
			wide and 6 rows tall (i.e. there will be 16 such blocks
			on the 32x12 SHARC-2 array).
			@See: 'blocks'

:: blocks		@Alias -> correlated.blocks
			@instrument: SHARC-2, SCUBA-2
			@Advanced
			Decorrelate on rectangular block regions of the array, 
			as a way to remove higher order sky-noise. As such, it 
			can be used together with, or instead of 'gradients'.
			@See: 'gradients', 'correlated.<?>'

:: boxes		@Alias -> correlated.boxes
			@Instrument: LABOCA
			@Advanced
			Decorrelate on electronic boxes, or set options for it.
			@See: 'correlated.<?>', 'cables', 'squids'

:: bright		Use for bright sources (S/N > ~1000). This setting
			entirely bypasses all filtering to produce a very
			faithful map. The drawback is more noise, but
			that should not be an issue for such a bright guy :-)
			Will invoke 'bright.cfg'.
			@See: 'config', 'faint', 'deep'

:: cables		@Alias -> correlated.cables
			@Instrument: LABOCA, ASZCA
			@Advanced
			Decorrelate channels whose signals are running on the 
			same cables, and which are therefore subject to the 
			same pickups (electromagnetic or microphonic).
			@See: 'correlated.<?>', 'boxes'

:: center		@Deprecated: 2.00-b4
			@See: 'pointing'

:: chirange=min:max	@Since: 2.31
			@Telescope: APEX
			@Expert
			A range of acceptable reduced chi values for 
			photometry. If a subscan cannot contribute photometry 
			within that range, it will not be part of the overall 
			photometry result.

:: chopped		Used for specifying a chopped data reduction. Can be
			set manually or automatically (via 'detect.chopped')
			based on the data itself. The key may trigger 
			conditional statements and extra decorrelation steps.
			@See: 'detect.chopped', 'correlated.<?>.trigger'

:: chopper		@Alias -> correlated.chopper-x
			@Instrument: SHARC-2
			@Advanced
			Remove signals that are correlated with chopper 
			movement. The moving secondary mirror changes the 
			telescope illumination, thus producing strong signals 
			when observing under a bright atmosphere. To first 
			order, such signals are linear with chopper 
			displacement. Since most telescopes chop in the 
			horizontal 'x' direction only, the 'chopper' keyword is
			aliased to decorrelation on motion in that direction. 
			When a 2D chopper is used, you should correlated.in 
			both the 'x' and 'y' directions.
			@See: 'correlated.<?>', 'detect.chopped'

:: chopper.invert	@Instrument: HAWC+
			@Expert
			@Since: 2.34
			An option to flip the direction associated with the
			analog chopper R/S signals. There was such an apparent
			flip between April and October 2016.

:: chopper.shift=N	@Instrument: HAWC+
			@Expert
			@Since: 2.34
			Shift the chopper R/S analog signals by N raw frames
			(sampled at 203.25 Hz), relative to the detector 
			readout to improve synchronization.
			@See: 'shift'

:: chopper.tolerance=X	@Instrument: HAWC+
			@Advanced
			@Since:2.34
			Allows setting a tolerance for the chopper position in
			arcsec. If the actual chopper distance is not within
			the tolerance from the nominal chopper amplitude, then 
			the exposure will not be used to avoid smearing.

:: clip=X		@Expert
			In early generations of the source map, force map
			pixels with flux below signal-to-noise level X to zero.
			This may help getting lesser baselines, and filtering 
			artefacts around the brighter peaks. Often used together
			with 'blank' in the intermediate iterations.
			@See: 'blank', 'iteration.[?]'

:: cols			@Alias -> 'correlated.cols'
			@Instrument: SHARC-2, p-ArTeMiS, HAWC+, SCUBA-2

:: conditions[=<pattern>]	@Since: 2.01-4
				Check conditional settings in the configuration
			Used without the pattern, it lists all conditionals
			under the current configuration tree. An optional
			pattern can be used to restrict the list to those
			conditions only, which start with the specified pattern.
			E.g.:

			   > crush [...] -condition=despike

			Will lists all conditions that depend on one of the
			despike settings ('despike', 'despike2', or 'despike3')
			Due to the configuration hierarchy, the listing can
			also be produces for subtrees. E.g.:

			   > crush [...] -date.conditions

			will list the conditions residing under the 'date'
			subtree (i.e. conditions originally specified as 
			'date.[...]').
			@See: 'poll', 'blacklist' 

:: config=<filename>	Load the configuration file filename. 
				The file is looked for in the locations in the
				following order:

					1. ./
					
					2. ./<instrument>/

					3. ~/.crush2/

					4. ~/.crush2/<instrument>/

			Whenever a matching file is found its contents are 
			parsed. Because of the ordering, it is convenient to 
			create overriding configurations.
			Thus instrument specific settings can be used to 
			override common defaults, and user specific settings 
			placed in '~/.crush2' can override the distribution 
			defaults. Whenever a configuration is parsed, there is 
			a note of it on the console output so that one always 
			knows which files were read and in what order. E.g. 
			when using
		
			   > crush laboca 12066

			the following configuration files will be loaded in 
			order (provided they exist):

			    <crush>/config/default.cfg
			    <crush/config/laboca/default.cfg
			    ~/.crush2/default.cfg
			    ~/.crush2/laboca/default.cfg
				  
			Each successively loaded file may override the options 
			set before it.
			When a matching configuration file is not found in any
			of the standard locations (above), CRUSH will make one
			last attempt to interpret the argument as a standard 
			pathname. This allows users to store and invoke custom 
			configurations anywhere on the file system.
			@See: 'bright', 'faint', 'deep'
	
:: convert		@Since: 2.01-3
			@Advanced

			@Instrument : SCUBA-2
			Just convert all the SDF files to FITS, then exit. 
			Batch conversion is useful if you are going to reduce
			the same dataset many times over (e.g. to optimize
			the reduction settings). You will need the 'ndf2fits'
			option to be configured and working, before batch 
			conversions can be used. The resulting FITS files are
			written to the path defined by 'outpath', or 'datapath'
			(in the above order, depending on which is defined). 
			@See: 'ndf2fits', 'outpath', 'datapath'

			@Instrument: MAKO
			The path to the executable that converts I/Q Fits
			into frequency shift, e.g. 'iqconv'.
			
:: correlated.<?>	Remove the correlated noise term accross the entire
			array. The <?> stands for the name of the modality on
			which decorrelation is performed. E.g. 'obs-channels', 
			'gradients', 'squids' (ASZCA, GISMO or SABOCA), or 
			'rows' (SHARC-2). 
			This is an effective way of dealing with most 
			atmospheric, and instrumental signals, such as sky 
			noise, ground pickup, temperature fluctuations, 
			electromagnetic or microphonic pickups. The 
			decorrelation of each modality can be further 
			controlled by a number of subkeys (see below). 
			The given decorrelation step must also appear in the
			pipeline 'ordering' before it can be used.
			@See: 'division', 'ordering', 'list.divisions'
				'list.response'

:: correlated.<?>.gainrange=min:max	@Expert
					Specify a range of acceptable gains to 
			the given correlated signal <?>, relative to the 
			average gain response of the correlated mode. Channels 
			that exhibit responses outside of this range will be 
			appropriately flagged in the reduction, and ignored in 
			the modeling steps until the flag is revised and 
			cleared in another decorrelation step.
			@See: 'division.<?>.gainflag', 'correlated.<?>.signed'

:: correlated.<?>.nofield	@Expert
				@since: 2.02
			Allows to decouple the gains of the correlated mode 
			from the gain fields stored under the channel (which 
			are initialized from the file specified by 
			'pixeldata'). 
			@See: 'pixeldata', 'source.fixedgains'

:: correlated.<?>.nogains	@Advanced
			      	Disable the solving of gains (i.e. channel 
				responses) to the correlated signal <?>.

:: correlated.<?>.nosignals	@Expert
				Disable the solving for correlated signal <?>, 
				whose value stays fixed afterwards.

:: correlated.<?>.phases	@Expert
				@Since: 2.02
			Decorrelated the phase data (e.g. for chopped
			photometry scans) together with the fast samples.
			The same gains are used as for the usual decorrelation
			on the fast samples.

:: correlated.<?>.phasegains	@Expert
				@Since: 2.04
			Determine gains from the phase data, rather than from
			the correlated fast samples. You can also set this
			globally for all correlated modalities/modes using
			the 'phasegains' keyword.
			Note, when the modulation is optical (such as a 
			chopping or waveplate stepping), phase-baed gains 
			should be derived for optically coupled modes only!
			@See: 'phasegains'

:: correlated.<?>.resolution=X	@Advanced
				Set the time resolution (in seconds) for the 
			decorrelation of <?>. When dealing with 1/f-type 
			signals, you probably want to set this to the 1/f knee 
			time-scale or below if you want optimal sensitivities. 
			Else, you may want to try larger values if you want to
 			recover more large-scale emission and you aren't too 
			worried about the loss of sensitivity.
			@See: 'extended'
			
:: correlated.<?>.signed	@Expert
				By default gain responses are allowed to be 
			bidirectional, and flagging affects only those channels
			or pixels, whose absolute gain values fall outside of 
			the specified range. When 'signed' is set, then gains 
			are flagged with the signs also taken into account. 
			I.e., under 'signed', 'gainrange' of '0.3:3.0' would 
			flag pixels with a gain of -0.8, whereas the default 
			behaviour is to tolerate them.
			@See: 'correlated.<?>.gainrange',
			      'correlated.<?>.nogains'

:: correlated.<?>.span		@Expert
				@Since: 2.02
			Make the gains of the correlated modality span scans
			instead of integrations (subscans). You can also
			set this option for all correlated modalities at once
			using the 'gains.span' key.
			@See: 'correlated.<?>.phases'

:: correlated.<?>.trigger=<key>	@Expert
				You can specify a configuration key that is to 
			serve as a trigger for activation the decorrelation of 
			<?>. This is used, for example to activate the 
			decorrelation of chopper signals, if and when the 
			'chopped' keyword is specified. E.g.:

			   chopper.trigger=chopped

			@See: 'chopper', 'chopped'

:: correlated.<?>.uniform	@Expert	
				@Since: 2.43
			Use uniform gains for this correlated modality,
			overriding any gains that may have been loaded or
			obtained prior.

:: correlated.*		@Advanced
			You can use wildcards '*' to set options for all
			decorrelation steps at once. E.g.:

			   correlated.*.resolution 1.0
			 
			Sets the time-resolution of all currently defined 
			decorrelation branches (and modalities) to 1 second.
			@See: 'correlated.<?>', 'resolution'

:: dataname.end=<list>	@Instrument: GISMO
			@Expert
			@Since: 2.05
			Allows specifying the naming convention of merged
			GISMO FITS files. E.g., the correct (and default) 
			setting for runs 1--4 is:

			   dataname.end GISO-IRAM-condensed.fits 

			To accomodate different naming conventions, the option
			can take a comma sparated list of possible endings,
			which are tried in order until a suitable match is
			found inside the scan directory.
			@See: 'datapath', 'object', 'date'

:: datapath=<dir>	Start looking for raw data in directory <dir>. Some
			instruments may also interpret it as a root directory
			in which data may reside some specific hierarchy. E.g.
			in <dir>/<project> for APEX bolometers. Thus, if an
			APEX instrument defines:
				
				datapath /homes/data
				project T-79.F-0002-2007

			then crush will try to find data first in
			'/homes/data', then in '/homes/data/T-79.F-0002-2007'
			This provides a convenient way for accessing 
			hierarchically stored data. See the instrument-
			specific notes for details.
 
:: dataunit=<name>	@Advanced
			Specify the units, in which the data are stored.
			Typically, 'counts' or 'V', or any of their common 
			multiples, such as 'mV', 'uV' or 'pcount' are accepted.
			The conversion from data units to jansky-based units is
	 		set via the 'jansky' option, while the choise of units 
			in the data reduction is set by 'unit'.
			@See: 'unit', 'jansky'

:: date=YYYY-MM-DD	@Instrument: GISMO, MAKO
			Specify the date of observation for GISMO data, which 
			can be used along with 'object' to help locate scan 
			data using scans numbers (and ranges). The date must be
 			given in the specified format, identical to the one 
			appearing in the standard IRAM scan IDs.
			@See: 'object', 'read'

:: date.[...]		@Advanced
			A way to set date specific conditional statements. 
			Inside the square brackets one can specify a date range 
			in YYYY-MM-DD format, separated by a colon ':' or 
			hyphen(s) '-'. Wildcards '*' are also accepted to 
			specify open ranges. E.g.:

			  date.[2009.12.10--*] instrument.gain=-1000.0

			Can be used to specify an inverted thousand-fold
			instrumental gain starting from Dec 10, 2009.
			@See: 'mjd', 'serial'

:: deep			Use for very faint sources which are not at all 
			detected in single scans, or if you think
			there is too much residual noise (baselines) in your 
			map to your liking. This setting results in the most 
			agressive filtering. Will load the configuration from
			'deep.cfg'. The output map is optimally filtered
			(smoothed) for point sources.
			@See: 'config', 'bright', 'faint'

:: dejump		@Since: 2.12
			@Expert
			Allows identifying places in the data stream where
			detectors jump together (esp. SQUIDs under a transient
			B-field fluctuation) by the perceived increase in 
			residual detector noise. Sub-settings are 'level'
			and 'minlength'
			@See: 'dejump.level', 'dejump.minlength', 'despike'

:: dejump.level=X	@Since: 2.12
			@Expert
			The relative noise level at which jumps are identified.
			The value should be strictly greater than 1, with 2.0
			being a safe starting point. Change with extreme 
			caution, if at all.
			@See: 'dejump'

:: dejump.minlength=X	@Since:2.12
			@Expert
			The minimum length (in seconds) of a coincident 
			detector jump that is kept alive in the data. Jumps
			longer than this threshold will be re-levelled, 
			wheareas shorter jumps will be flagged out entirely.
			@See: 'dejump'
 
:: despike		Use despiking. CRUSH allows the use of up to three
	 		different despiking steps, each configurable on its
			own, to specify a despiking method, S/N level and
			flagging criteria. See the various despiking options
			below:

:: despike.blocks	@Expert
			@Since: 2.33
			Flag out an entire 'drifts' block of data around 
			any spikes found. This is probably an overkill in most
			cases, but may be useful if spikes are due to 
			discontinuities (jumps) in individual detectors.
			@See: 'drifts'
			
:: despike.flagcount=N	@Expert
			Tolerate (w/o pixel flagging) up to N spikes up in each
	 		pixel.

:: despike.flagfraction=X	@Expert
				Tolerate (w/o pixel flagging) spikes up to 
			fraction X of the scan frames in each channel.
				
:: despike.framespikes=N	@Expert
				Tolerate up to N spikes per frame.
	
:: despike.level=X	@Advanced
			Despike at an S/N level of X.	

:: despike.method=<name>	@Advanced
				CRUSH offers a choice of despiking methods to 
			choose from. Each of these have their own pros and 
			cons, and may produce different results and side-
			effects in different environments. The following 
			methods are currently available:

			   neighbours  Despike only by comparing neighbouring 
			   	       samples of data from the same channel.

			   absolute    Flag data that deviates by the specified
			   	       S/N level.

			   gradual     Like 'absolute' but proceeds more 
			   	       cautiously, removing only a fraction of
				       most offending spikes at each turn.

			   multires    Look for spikes wider than just a sigle 
			   	       sample. 

			All methods will flag pixels and frames if these have 
			too many spikes. The flagging of spiky channels and 
			frames is controlled by the 'flagcount, 'flagfraction' 
			and 'framespikes' subkeys.
			@See: 'despike.flagcount', 'despike.flagfraction',
			      'despike.framespikes', 'despike.level',

:: despike.phases	@Expert
			@Since: 2.43
			@Was: 'phasedespike' (2.15 - 2.42)
			When set, the phase data (such as position-switched
			phases) will be despiked together with the regular
			high-frequency despiking. The despiking level is the
			same as for the 'despike' option.
			@See: 'despike', 'despike.level', 'weighting.phases'

:: detect.chopped	@Advanced
			Try determine from the data itself if the chopper was 
			used, and set the 'chopped' flag accordingly. This can 
			be used to trigger the actication of specific reduction
			steps for chopped data.
			@See: 'correlated.<?>.trigger'

:: distortion		@Expert
			@Since: 2.14
			@Instrument: MAKO ...
			Correct nominal pixel positions for the 2D focal-plane
			distortion.
			@See: 'distortion.x??', 'distortion.y??', 
			      'distortion.unit', 'distortion.name'

:: distortion.name=<name>	@Expert
				@Since: 2.30
			Provide a name for the distortion model that helps 
			identify it to the user. The distortion model will work
			just fine without a name too...

:: distortion.unit=<name>	@Expert
				@Since: 2.14
				@Instrument: MAKO ...
			The unit in which focal plane positions are defined for
			the distortion coefficients. E.g. 'arcsec'. If not
			specified, unity (or dimensionless) is assumed.
			@See: 'distortion', 'distortion.x??', 'distortion.y??'

:: distortion.x<nm<	@Expert
			@Since: 2.14
			@Instrument: MAKO, SCUBA-2
			Define a distortion coefficient for the x-coordinate.
			'x' is followed by two integers n and m (0-9) defining 
			the x,y exponents of the distortion term for which this
			coefficient applies. E.g.: x31 specifies the term
			
				dx = x31 * x^3 * y^1

			dx, x, and y are all in the units defined by
			'distortion.unit'

			@See: 'distortion.y<nm>', 'distortion', 
			'distortion.unit', 'distortion.name'

:: distortion.y<nm>	@Expert
			@Since: 2.14
			@Instrument: MAKO ...
			Same as 'distortion.x<nm>' but for calculating 
			distortion in the y-direction.
			@See: 'distortion.x<nm>'

:: division.<?>=<list> 	@Expert
			Specify a new pixel division <?> from a list of pixel 
			groups, separated by commas. For example, if the pixel 
			groups 'my-pixels-1' and 'my-pixels-2' were defined 
			(via 'group.<?>') then the line

			   division.my-division my-pixels-1,my-pixels-2
			   
			creates a division from these two groups. For every
			division created this way, CRUSH will also create a
			correlated modality with the same name.
			@See: 'correlated.<?>', group.<?>, 'list.divisions'
				'list.response' 

:: division.<?>.id=<ID>	@Expert
			Specify a designated ID for the pixel division <?>. 
			This short ID will be printed on the console output, 
			whenever the decorrelation step on the modality <?> is 
			performed in the reduction.
			@See: 'correlated.<?>'

:: division.<?>.gainfield=<name>	@Expert
					You can also specify the name of an 
					existing JAVA double field inside the
			pixel class of the given instrument to serve the gains
			for the decorrelation of <?>. Unless 
			'correlated.<?>.nogains' is also specified, these gains
			will be determined and overwriten each time the 
			decorrelation takes place.
			@See: 'correlated.<?>.nogains'

:: division.<?>.gainflag=N	@Expert
				Specify a gain flagging pattern to use when 
				flagging outlying gains in the decorrelation 
			step of <?>. Gain flags are normally one bit in a 
			4-byte integer, and can be specified using octal ('0' 
			prefix) or hexadecimal ('0x' prefix) numbers, and 
			regular integers. You should be careful not to 
			interfere with existing flags, many of which may be
			hardcoded in the JAVA source. Use with extreme caution,
			if you must...
			@See: 'correlated.<?>.gainrange'

:: downsample=X		@Advanced
			Downsample the data by a factor of N. At times the
			raw data is sampled at unnecessarily high frequencies.
			By donwsampling, you can ease the memory requirement
			and speed up the reduction. You can also set the value
			to 'auto' (default), in which case an optimal 
			downsampling rate is determined based on the typical 
			scanning speeds, s.t. the loss of information will be 
			insignificant due to unintended smearing of the data.

:: drifts=X		@Advanced
			Filter low frequencies below the characteristic 
			timescale of X seconds. An effective way of dealing 
			with 1/f noise.
			You can also use 'auto' to determine the filtering
			timescales automatically, based on 'sourcesize', 
			scanning speeds, and instrument 'stability' time-scales.
			@Version: 2.12
			As of version 2.12, the value 'max' is also accepted
			producing results identical to that of 'offsets'.
			@See: 'sourcesize', 'stability', 'offsets'

:: drp			@Advanced
			@Instrument: HAWC+
			@Since: 2.30-4
			Turn on DRP messages through TCP/IP. Enabling this 
			option will let crush know that is it being run as part
			of the standard HAWC+ Data Reduction Pipeline (DRP),
			to which it can send status updates as the reduction 
			proceeds.		
			@See: 'drp.host', 'drp.port', 'drp.id', 'drp.timeout'

:: drp.fifo=N		@Expert
			@Instrument: HAWC+
			@Since: 2.30-4
			Set the DRP FIFO size to max. N queued outgoing 
			messages.

:: drp.host=<name>	@Expert
			@Instrument: HAWC+
			@Since: 2.30-4
			Specify the hotname to send DRP messages to, if it
			is not 'localhost' or '127.0.0.1'
			@See: 'drp.port', 'drp.timeout'

:: drp.id=<ID>		@Expert
			@Instrument: HAWC+
			@Since: 2.30-4
			Set the message origination ID to the specified value.
			E.g.:

			  drp.id=hawc.pipe.crush

			Will send messges with sender ID 'hawc.pipe.crush'.

:: drp.port=N		@Expert
			@Instrument: HAWC+
			@Since: 2.30-4
			Specify the port oto which DRP messages are sent, if
			it is not the default 50747.
			@See: 'drp.host'

:: drp.timeout=X	@Expert
			@Instrument: HAWC+
			@Since: 2.30-4
			Set the DRP socket timeout to X seconds. If the DRP
			message cannot be sent within this timeframe, CRUSH
			will stop sending DRP messages for the rest the 
			reduction.
			@See: 'drp.host', 'drp.port'

:: drp.timestamp	@Expert
			@Instrument: HAWC+
			@Since: 2.30-4
			If the option is specified, DRP messages will have
			a timestamp attached to the end of message. An '@' 
			character will mark the end of message, and the
			beginning of the timestamp.

:: echo=<text>		@Advanced
			@Since: 2.12
			Print <text> onto the error stream. This <text> can
			include references to other settings, environment
			variables or Java properties. The <text> value will 
			appear on the error stream as soon as the echo 
			statement is parse by CRUSH, making 'echo' a useful
			tool for checking if and when configuration values are
			actually loaded.
			@See: 'poll'

:: ecliptic		@Alias -> system=ecliptic
			Reduce using ecliptic coordinates (for mapping).
			@See: 'system', 'altaz', 'equatorial'

:: elevation-response   @Instrument: SHARC-2, MAKO
			@Expert
			Load and use an lookup table for the elevation 
			dependent forward efficiency of the telecscope. The 
			table is an ASCII file, as specified by Darren Dowell, 
			and is available from the SHARC-2 web-site. CRUSH 
			contains copies of the available tables and is 
			configured to use them as needed.

:: env.[]		@Since: 2.34
			@Advanced
			Set options conditionally based on the shell 
			environment from which CRUSH is invoked. Inside the
			backets, four kind of options may appear. These are:

			  1. Existence of an environment variable. E.g.
		
			     env.[HOME] 	# true if HOME exists
			
			  2. Non-existence of a variable. E.g.

			     env.[!HOME]	# true if HOME is undefined.	

			  3. If a variable is set to a specific value. E.g.
	
			     env.[HOSTNAME?bar]  # true if HOSTNAME is 'bar'

			  4. If a variable is set to any other value. E.g.
			
			     env.[HOSTNAME?!bar] # true if HOSTNAME isn't 'bar'

			Note, that since CRUSH options are case insensitive, in
			general, but because evironments are not necessarily
			so, CRUSH will assume that the names of variables
			exists in upper case (ALWAYS!), whereas their values
			are matched case insensitive. Thus, 'env.[home]' and 
			'env.[HOME]' both check the existence of 'HOME'.
			@See: 'property.[]' 

:: epoch=X		@Instrument: GISMO
			Normally the coordinate epoch, in which the equatorial 
			source coordinates are expressed, is stored in the data.
			However, for GISMO runs 1 and 2, this information was 
			handled incorrectly. This option provides the means to 
			correct that. The value can specify a year (e.g. 
			1950.0, or 2000.0), or a proper epoch designation 
			(e.g. B1950, or J2000). IRAM uses J2000 for static 
			sources and the current epoch for solar system objects.

:: equatorial		@Alias -> system=equatorial
			Reduce using equatorial coordinates (for mapping).
			@See: 'system', 'altaz'

:: estimator=<type>	@Advanced
			'median' or 'maximum-likelihood' estimators to use in 
			deriving signal models. 'median' estimators are less 
			sensitive to the presence of bright sources in the 
			data, therefore it is the default for when 'bright' is 
			specified (see 'bright.cfg'), and for some instruments 
			(e.g. GISMO).
			When medians are used, the corresponding models are 
			reported on the console output in []'s...
			(see the Console Output section of the README).
			@See: 'gains.estimator', 'weighting.method'

:: exposureclip=X  	@Advanced
			Flag (clip) map pixels whose relative time coverage
			is less than the specified value X. This is helpful for
			discarding the underexposed noisy edges of the map.
			@See: 'noiseclip', 'clip'

:: excessload=X		@Instrument: SHARC-2
			@Expert 
			SHARC-2 can determine a line-of-sight opacity based on 
			the total-power response of its detectors. However, for 
			this to work well, all sources of optical loading on 
			the detectors must be understood. The load curves (see 
			'response') were determined at one time only, and 
			therefore this flag provides the means to specify a
			different optical loading environment from then, as an
			excess optical load (in Kelvins).
			@See: 'response', 'tau.<?>'

:: extended		Try to better preserve extended structures. This
			setting can be used alone or in combination with
			a brightness options. The fainter settings the more 
			difficult it is to recover extended emission. For 
			bright structures recovery up to FOV (or beyond!) 
			should be possible, while for faint structures ~1/4 FOV
			to ~FOV scales are maximally obtainable (see more on 
			this in the README).
  			@See: 'sourcesize', 'bright', 'faint', 'deep'

:: faint		Use with faint sources (S/N < ~30) when the
			source is faint but still visible in a single scan. 
			This setting applies some more aggressive filtering of 
			the timestreams, and extended structures. It invokes 
			'faint.cfg'.
			@See: 'bright', 'deep'

:: fazo			@Telescope: CSO
			An alternative to 'center' for providing pointing 
			corrections. As opposed to 'center', which specifies 
			incremental corrections, this option takes an absolute 
			AZ pointing offset (i.e. FAZO at the CSO) which should 
			have been the correct one (as opposed to the value used
			by the antenna computer during the observations).
			@See: 'fzao', 'center'

:: febe			@Telescope: APEX
			@Expert
			Defines the frontend-backend combination to use. 
			E.g. for LABOCA, this would be set to 'LABOCA-ABBA'.

:: fillgaps		@Since: 2.30
			@Advanced
			Fill any gaps in the timestream data with empty frames
			so that time windows in the reduction work as expected
			and that no surprise discontinuities can cause real
			trouble.

:: filter		@Since: 2.10
			@Advanced
			Activate spectral filtering of time-streams. The 
			filter components are set by 'filter.ordering' and can
			be configured activated separately.
			@See: 'filter.ordering', 'filter.hwp', 'filter.motion', 
			'filter.kill', 'filter.whiten'

:: filter.hwp		@Instrument: PolKa
			@Advanced
			@Since: 2.11
			Use FFT filtering to get rid of the total-power
			modulation by the half-waveplate rotation. Can be used
			together with, or instead of, 'purify'. The advantage
			of the FFT filtering is that it works even if the 
			waveplate data is not entirely accurate (i.e. jittery).
			However, if the waveplate phase is fully known, then
			'purify' should be the prefered method for rejecting
			the unwanted total-power modulation. The number of
			harmonics (over the rotation frequency) is controlled
			by the 'harmonics' subkey.
			@See: 'filter.hwp.harmonics', 'waveplate.jitter'
			      'purify', 'waveplate.frequency'

:: filter.hwp.harmonics=N	@Instrument: PolKa
				@Expert
				@Since: 2.11
			Specify how many harmonics of the waveplate rotation
			frequency to use in the half-waveplate filter.
			@See: 'filter.hwp'

:: filter.kill		@Since: 2.10
			@Expert
			Allows completely quenching certain frequencies in the
			time-stream data. To activate, both this option and the
			'filter' umbrella option must be set. The bands of the
			kill-filter are set by 'filter.kill.bands'.
			@See: 'filter', 'filter.kill.bands'

:: filter.kill.bands=<list>	@Since: 2.10
				@Expert
			Provide a comman-separated list of frequency ranges
			(in Hz) that are to be quenched by the kill-filter. 
			E.g.:

			  filter.kill.bands 0.35--0.37, 9.8-10.2
			
			@See: 'filter', 'filter.kill'

:: filter.motion	@Since: 2.10
			@Advanced
			The (typically) periodic motion of the scanning can
			induce vibrations in the telescope and instrument. 
			Since these signals will be in synch with the scanning 
			motion they will produce definite mapping artefacts
			(e.g. broad peaks or bowls in the map center, or ridges
			near the map edges). The motion filter lets you
 			spectrally filter those frequencies where most of the
			scanning motion is concentrated. To activate, both this
			option and the 'filter' umbrella option must be set.  
			The identification of rejected motion frequencies is
			controlled by the 's2n', 'above', and 'range' sub-keys
			@See: 'filter', 'filter.motion.s2n',
			'filter.motion.above', 'filter.motion.range'

:: filter.motion.above=X	@Since: 2.10
				@Expert
			The fraction, relative to the peak spectral component
			of the scanning motion, above which to filter motion.
			E.g.:
			  
			  filter.motion.above 0.1

			will identify component that have amplited at least 10%
			of the main component.
			@See: 'filter.motion', 'filter.motion.s2n', 
			'filter.motion.range'

:: filter.motion.harmonics=n	@Since:2.15-2
				@Expert
				Kill not just the dominant motion frequencies
				but also up to n harmonics of these. This may
			be useful when the motion response is non-linear. 
			Otherwise it's an overkill.
			@See: 'filter.motion.odd'

:: filter.motion.odd	@Since:2.15-2
			@Expert
			When defined, together with the 'harmonics' setting,
			this option instructs crush to restrict the motion
			filter to the odd harmonics only of the principal
			frequencies of the scanning motion.
			@See: 'filter.motion.harmonics'	

:: filter.motion.range=min:max	@Since: 2.10
				@Expert
			Set the frequency range (Hz) in which the motion filter
			operates.
			@See: 'filter.motion', 'filter.motion.above',
			'filter.motion.s2n'

:: filter.motion.s2n=X		@Since: 2.10
				@Expert
			The minimum significance of the motion spectral 
			component to be considered for filtering.
			@See: 'filter.motion', 'filter.motion.above', 
			'filter.motion.range'

:: filter.motion.stability=X	@Since: 2.15-2
				@Expert
				Define a stability timescale (in seconds) for
				the motion response. When not set, it is 
			assumed that the detectors respond the same amount to
			the vibrations induced by the scanning motion during
			the entire duration of a scan. If a timescale shorter
			than the scan length is set, then the filtering will
			become more aggressive to incorporate the AM modulation
			of detector signals on timescales shorter than this
			stability value.
			@See: 'filter.motion.range', 'filter.motion.stability'	

:: filter.mrproper	@Expert
			@Since: 2.23
			Enables the explicit re-levelling of the filtered 
			signal. In practice, the re-levelling is unlikely to
			improve significantly on the filter's effectiveness. At
			the same time, it does slow it down somewhat, which is
			why it has been turned off by default starting in 2.23.


:: filter.ordering=<list>	@Since: 2.10
				@Expert
			A comma-separated list of spectral filters, in the
			order they are to be applied. E.g., the default is:
			
			  filter.ordering motion, kill, whiten

			applies first the motion filter, then kills specified
			spectral bands, and finally applies noise whitening
			on the remainder. Each of the components can be 
			controlled and activated separately with the 
			appropriate subkeys of 'filter' with the same names.
			@See: 'filter.motion', 'filter.whiten', 'filter.kill'
				
:: filter.whiten	@Since: 2.10
			@Was: 'whiten'
			@Advanced
			Use noise whitening algorithm. White noise assures that
			the noise in the map is independent pixel-to-pixel. 
			Otherwise noise may be correlated on spacific scales.
			Whitening is also useful to get rid of any signals
			(still) unmodelled by the other reduction steps. It
			should always be a last resort only. The modeling of
			signals is generally preferred. To activate, both this
                        option and the 'filter' umbrella option must be set.
			@See: 'filter', 'whiten', 'filter.whiten.below', 
			'filter.whiten.level', 'filter.whiten.minchannels'
			'filter.whiten.proberange'
			
:: filter.whiten.below	@Since: 2.10
			@Was: 'whiten.below'
			@Expert
			By default the whitening filter only supresses
			excessive noise, but will leave those spectral 
			components untouched, where the spectral power is
			deficient. Setting this option allows the boosting of
			such components to the white level, thus achieving
			true noise whitening, which is necessary to obtain maps 
			without instrinsic spacial correlations.
			@See: 'filter.whiten', 'filter.whiten.below.max'

:: filter.whiten.below.max=X	@Since: 2.10
				@Expert
			The maximum boosting of spectral power that may be
			applied when whitening frequencies with a deficiency
			of signal below the white level. The option acts as
			a safety pin, making sure that whitening does not
			enhance spectral bands insanely, when 
			'filter.whiten.below' is enabled.
			@See: 'filter.whiten.below'

:: filter.whiten.level=X	@Since: 2.10
				@Was: 'whiten.level'
				@Advanced
			Specify the noise whitening level at X times
			the average (median) spectral noise level. 
			Spectral channels that have noise in excess of the
			critical level will be approproately filtered to bring
			them back in line. Values clearly above 1 are 
			recommended. Typically values around 1.5--2.0 are 
			useful without overfiltering.
			@See: 'filter.whiten'

:: filter.whiten.minchannels=N	@Since: 2.10
				@Was: 'whiten.minchannels'
				@Expert
			Make sure that at least N channels are used for
			estimating the white noise levels, even if the 
			specified probe range is smaller or falls outside of
			the available spectrum. In such cases, CRUSH will
			automatically expand the requested range to include
			at least N spectral channels, or as many as possible
			if the spectral range itself is too small.
			@See: 'filter.whiten', 'filter.whiten.proberange'
	
:: filter.whiten.proberange=from:to	@Since: 2.10
					@Was: 'whiten.proberange'
					@Expert
			Specify the spectral range as <from>:<to> (in Hz), 
			in which to measure the white-noise level before 
			whitening. It is best to use the truly flat part of the
	 		available spectral range, with no 1/f, resonances or 
			lowpass roloff are present. Wildcards '*' can be used 
			for specifying open ranges.
		
                        @Since: 2.14
			Introduced 'auto' setting, to adjust the probing range
			automatically to the upper part of the spectrum
			occupied by point sources.

			@See: 'filter.whiten', 'filter.whiten.minchannels'
		

:: final:key=value	@Alias -> iteration.[last]
			When used on the command line, a ':' can be used as
			a sepatation between the abbreviated condition and its
			statement. E.g.:

			   > crush [...] -final:smooth=beam

			to specify beam smoothing in the last iteration.

:: fits.[key]
:: fits.[key?value]	@Advanced
			@Since: 2.23
			Conditions based on the existence of specific FITS keys
			in the input scan headers, or based on these keys 
			having specific values. Both the keys and the 
			comparison to expected values is case insensitive. Thus,
			for example, the existence of 
	
				OBJECT = 'Mars' 

			in the  FITS header will activate the conditional 
			'bright' reduction setting defined as:

				fits.[object?MARS] bright

:: fits.addkeys=<list>  @Telescope: SOFIA
                        @Expert
                        @Since: 2.23
                        Specify a comma-separated list of keys that should be
                        migrated from the first scan to the image header, in
                        addition to the list of required SOFIA header keys.

:: fits.assing.<key> <option>	@Advanced
				@Since: 2.34
				Associate the values of FITS keys to CRUSH
			configuration options directly. The assignment will 
			happen when the input FITS files are read.
		
:: fixjumps		@Instrument: HAWC+
			@Since: 2.34
			@Expert
			Attempt to 'fix' residual flux jumps that result from
			imprecise correction in the MCE. Long jumps are
			re-levelled, while shoter ones are flagged out to
			minimize impact on source structure. Alternatively,
			the same can be applied on a per-sibarray basis as
			well via the 'fixjumps.<sub>' option.
			@See: 'fixjumps.<sub>'

:: fixjumps.<sub>	@Instrument: HAWC+
			@Since: 2.34
			@Expert
			Same as 'fixjumps' but performed on a per-subarray
			basis. e.g. 'fixjumps.R1' will apply the fix to the
			R1 subarray.
			@See: 'fixjumps'
	
:: flag=<list>		Specify a list of channels that ought to be ignored. 
			Can use instrument-specific pixel IDs, fixed indices 
			(usually data storage indexes) and ranges. E.g.:

			   flag 5-10,12,33-37

			or

			   flag R0[13,6]-R0[13,29],T1[0,0]	# {HAWC+}
			   
			Fixed indices normally start at 1 (i.e. not C-style!).
			@See: 'noslim', 'blind' 

:: flatweights		@Since: 2.14
			@Advanced
			Override the channels weights from 'pixeldata' with
			their average value. This way all channels carry the
			same uniformized initial weight. It can be useful when
			the 'pixeldata' weights are suspect for some reason.
			@See: 'pixeldata'


:: flight=N		@Telescope: SOFIA
			@Since: 2.33
			Set the flight number for locating data files using
			scan numbers only. Remember to set 'datapath' also to
			specify the folder where scan files are stored.
			@See: 'datapath'


:: focalplane		@Alias -> system=focalplane
			@Since: 2.14
			@Expert
			Produce maps in focal-plane coordinates. This is 
			practical only for beam-mapping. Thus, focal-plane
			coordinates are default when 'source.type' is set to
			'pixelmap'
			@See: 'pixelmap', 'source.type'

:: forget=<list>...	Forget the priorly set values for the listed options 
			as if they were never defined. E.g. 
		     		
			   forget=outpath

			will unset the 'outpath' option. You can specify more 
			than one options as a comma-separated list. E.g.
	
			   forget=outpath,project
				
			Will unset both the 'outpath' and 'project' options.	
			Forgotten values may be 'recall'-ed.
			Additionally, 'forget' can be used to clear all
			conditionals or all blacklisted settings, if the
			argument list contains the values 'conditions' or 
			'blacklist', respectively.
			@See: 'recall', 'blacklist', 'remove'

:: frames=<from>-<to>   @Advanced
			Read only frames <from>-<to> from the data. Maybe
			useful for quick peeks at the data without processing
			the full scan, or when a part of the data is corrupted.

:: fzao			@Telescope: CSO
			Specify a zenith pointing offset.
			@See: 'fazo'

:: gain=X     		@Expert
			Specify an instrument gain of X from the detector stage 
			(or fixed signal stage) to the readout. Many 
			instruments may automatically determine the relevant 
			gain based on their data headers. For others, the gains
			may have to be adjusted by hand, especially if they are
			changing. Upon reading the scans, CRUSH will divide all
			data by the specified value, to bring all scans to a 
			comparable signal level. Conversions to 'jansky' are 
			referenced to such gain-scaled data.
			@See: 'jansky', 'dataunit', 'scale'

:: gainnoise		@Expert
			Add noise to the initial gains. There isn't much use
			for this option, other than it allows to check the
			robustness of the reduction on the initial gain 
			assumption. Since gains are usually measured in the
			reduction itself, typical reductions should not depend
			a lot on the intitial gain values.
			@See: 'uniform'

:: gains		@Advanced
			Solve for pixel gains based on their response to the
			correlated noise (above). If not specified, then
			all decorrelation steps will proceed without gain 
			solution. A model-by-model control is offered by the
			'correlated.<?>.nogains' option.
			@See: 'gains.estimator', 'correlated.<?>.nogains'

:: gains.estimator=<type>	@Advanced
				Specify the type of estimator ('median' or
				'maximum-likelihood') to be used for estimating
			pixel gains to correlated signals.
			@See: 'estimator', 'correlated.<?>'
			
:: galactic 		@Alias -> system=galactic
			Reduce using new galactic coordinates (for mapping).
			@See: 'system', 'equatorial', 'altaz'

:: gnuplot=<path>	@Since: 2.14
			The path to the gnuplot executable, if available.
			Some reduction modes (e.g. skydip reductions) may use 
			'gnuplot' to plot the result. Both PNG and EPS outputs
			may be produced, depending on whether 'write.png' 
			and/or 'write.eps' are set.
			@See: 'skydip', 'write.eps', 'write.png'

:: gradients		@Alias -> correlated.gradients
			@Advanced
			Shorthand for the decorrelation of gradients accross the
			detector array. Such gradients can occue as a result of
			spatial sky-noise, or as temperature variation across 
			the detectors.
			@See: 'correlated.<?>', 'blocks'			
	
:: grid=X		set the map pixelization to X arcsec. Pixelization
			smaller than 2/5 beam is recommended. The default is
			~1/5 beam pixelization.

:: grid=dx,dy		@Since: 2.16-1
			@Advanced
			Set a non-square map pixelization. Not all FITS viewers
			support it though...

:: group.<?>=<list>     @Expert
			Specify a list of channels, by IDs, fixed index 
			(usually same as storage index), or ranges thereof, 
			that ought to belong to a group with name <?>. The
			argument is a comma separated list E.g.:

			  group.my-group 10-20,45,50-60

			or

			  group.my-group R1[5,11]-R1[5,15],T0[12,2]   # {HAWC+}
			    	
			defines a group named 'my-group' from the specified
			channels.
			@See: 'division'

:: gyrocorrect		@Instrument: HAWC+
			@Since: 2.41
			@Advanced
			Correct for gyro drifts based on guide-star relock
			data stored in the scan headers. This isn't normally
			needed when the gyros funtion properly. But, 
			occasionally, they drift a fair bit, and this option
			can activate the correction scheme on demand.
			@See: 'gyrocorrect.max'

:: gyrocorrect.max=X	@Instrument: HAWC+
			@Since: 2.41
			@Expert
			Set a limit to how large of a gyro drift (X in arcsec)
			can be corrected for. When drifts larger than that are
			found in a scan, then the correction is skipped for
			single scan reductions (perhaps it's just a fluke)
			or dropped from the set in multi-scan reductions
			(to be safe).

:: gzip			@Since: 2.42
			Compress the output (e.g. FITS) with gzip, if possible.
			(The output file name will have .gz extention added as 
			needed.)

:: he3=<source>		@Instrument: LABOCA
			@Advanced
			Correct time-streams for He3 temperature fluctuations. 
			<source> specifies the source of the He3 data, which 
			can be 'thermistor' or 'blinds'. The use of blind 
			bolometers is quicker and preferred, unless you 
			specifically wish to use the 'thermistors'.

:: he3.gains		@Instrument: LABOCA
			@Expert
			Specifies that rather than correcting for temperature 
			fluctuations, the thermistor and bolometer data should 
			be used to calculate appropriate temperature gains. 
			This option should only be used on skydip scans with 
			the shutter closed (i.e. only temperature signals 
			without sky). Additionally 'forget=source' should be 
			used to disable source modeling for such data.

:: he3.maxrms=X		@Instrument: LABOCA
			@Expert
			Define the maximum RMS temperature variation (Kelvin)
			over the duration of a scan. When a scan has variation
			larger than this limit, it will be dropped from the
			reduction. 
	
:: horizontal		@Alias -> system=horizontal
			Reduce in horizontal coordinates (for mapping).
			This is often useful for determining pointing offsets
			or for pixel location mapping.
			@See: 'system', 'center', 'pixelmap', 'fazo', 'fzao'

:: id.[<range>]		@Instrument: GISMO
			@Advanced
			@Since: 2.12-b1
			Set conditions based on IRAM Scan ID ranges (of format
			'YYYY-MM-DD.nnn'. Asterix ('*') denotes an open-ended
			range as usual. The lower bound is inclusive, but the
			upper bound is not. 

			E.g.:

			  id.[2012-04-11.132:2012-04-12.23] jansky 32.8
			  id.[2012-04-14.25:*] janky 28.6 			
					
			Sets different conversion factors (counts/Jy) for the
			two id ranges. Note, that the first range does not 
			include scan 23 taken on 2012-04-12 itself. The second
			line shown an open-ended range starting with scan 25
			on 2012-04-14.
			@See: 'mjd.[]', 'serial.[]', 'date.[]' 

:: idle=N		@Since: 2.15-2
   idle=x%		Instruct crush to avoid using N number of CPU cores, or
			x percent of the available processors. By default crush
			will try to use all processing cores in your machine 
			for maximum performance. This option allows to modify 
			this behavior according to need. 
			Note, that at least 1 CPU will always be used by crush, 
			independent of this setting. The number of actual 
			parallel threads will be the smaller of the allowed 
			number of CPUs and the number of scans processed.

:: imaging.aperture=X[,Y]    

			@Instrument: HIRMES
			@Expert
			@Since: 2.42
                        Specifies the imaging aperture size, either as a square
                        of X arcseconds size, or a rectangle of X by Y arcsec.

:: indexing		@Expert
			Allows the use of data indexing to speed up coordinate
			calculations for mapping. Without indexing the map
			coordinates are calculated at each mapping step. This 
			can be slow because of the complexity of the spherical
			projections, which often require several complex math
			evaluations. With indexing enabled, the calculations
			are performed only once, and the relevant data is stored
			for reuse. However, the storage of indexes more or
			less doubles the memory requirement of CRUSH. Thus, 
			'indexing' may be disabled for very large reductions.
			Alternatively, one may control the amount of memory such
			indexes may use, via the 'indexing.saturation' option.
			@See: 'indexing.saturation', 'grid'

:: indexing.saturation=X 	@Expert
				Specify the maximum fraction X of the total
				available memory that can be filled before
			indexing is automatically disabled. Given a typically 
			20% overhead during reduction, values below 0.8 are
			recommended to avoid overflows. 
			@See: 'indexing'

:: invert		Invert signals. This setting may be useful in creating 
			custom jackknifes, where the user wishes to retain 
			control over which scans are inverted.
			@See: 'gain', 'scale', 'jackknife'

:: iteration.[N]	Use as a condition to delay settings until the Nth
			iteration. E.g.

			   iteration.[3] smooth halfbeam

			or 

			   > crush [...] -iteration.[3]smooth=halfbeam [...]
			 
			to specify half-beam smoothing starting from the 3rd
			iteration.
			@See: 'iteration.[?]'

			
:: iteration.[last]    	Specify settings that should be interpreted only at the 
			beginning of the last iteration.
			@See: 'iteration.[?]'
	
:: iteration.[last-N]  	Activate settings N iterations before the last one. 
			E.g.
			    
			    iteration.[last-2] forget=clip

			Disables clipping two iterations before the last one.	
			@See: 'iteration.[?]'

:: iteration.[X%]	Activate settings as a percentage X of the total
			number of iterations (as set by 'rounds'). E.g.
			
			    iteration.[50%] forget clip

			can be used to disable the S/N clipping of the source 
			map half way through the reduction.
			@See: 'iteration.[?]'

:: iteration.[?]	Apply settings at the beginning of specific iterations. 
			Because of the flexible syntax, the same iteration can 
			be referred to in different ways. Consider a reduction 
			with 10 rounds. Then,

			    iteration.[5] smooth 5.0
			    iteration.[50%] smooth 10.0
			    iteration.[last-5] smooth beam

			can all be used to define what happens in the 5th
			iteration. CRUSH will parse these conditionals in the 
			above order: first the explicit iteration settings then 
			those relative to the reduction length, and finally the 
			settings relative to the end of the reduction. Thus, in 
			the above example the beam smoothing will always 
			override the other two settings.
			@See: 'iteration.[N]', 'iteration.[X%]', 
			      'iteration.[last]', 'iteration.[last-N]'


:: jackknife		Jackkniving is a useful technique to produce accurate 
			noise maps from large datasets. When the option is used 
			the scan signals are randomly inverted, s.t. the source 
			signals in large datasets will tend to cancel out, 
			leaving one with pure noise maps.
			The sign inversion is truly random, s.t. repeated runs
			with the 'jackknife' flag will produce a different 
			jackknife every time. If you want more control over 
			which scans are inverted, consider using the 'invert' 
			flag instead.
			@See: 'invert', 'scramble', 'jackknife.frames', 
			      'jackknife.channels', 'jackknife.alternate'

:: jackknife.alternate	@Advanced
			@Since: 2.05
			Rather than randomly inverting scans for a jackknife,
			this option will invert every other scan. This may be
			preferred for small datasets, because it leads to
			better cancellation of the source signals, especially
			with an even number of scans, chronologically listed.
			To have the desired effect, use instead of 'jackknife',
			rather than together with it (otherwise, the ordered 
			inversion will simply compound the random method of the
			standard 'jackknife').
			@See: 'jackknife'

:: jackknife.channels	@Expert
			@Since: 2.04
			Jackknife channels, such that they are randomly 
			inverted for the source model. Beware, however, that 
			channel-wise jackknives aren't as representative of the
			true noise as the regular scanwise 'jackknife' is, 
			because they will reject spatial correlations and
			instrumental channel-to-channel correlations.
			@See: 'jackknife', 'jackknife.frames', 'scramble'

:: jackknife.frames	@Expert
			@Since: 2.04
			Jackknife frames, such that they are randomly inverted
			for the source model. Beware, however, that frame
			jackknives aren't as representative of the true noise
			as the regular scanwise 'jackknife' is, because they
			will reject temporal correlations.
			@See: 'jackknife', 'jackknife.channels', 'scramble'

:: jansky=X		Specify the calibration factor from data units to Jy.
			@See: 'dataunit', 'gain', 'jansky.inverse'.

:: jansky.inverse	When used, the 'jansky' definition is inverted to mean
			Jy to data unit. This used to be the old definition used
			in crush-1.xx and minicrush.
			@See: 'jansky'

:: K2Jy=X		@Advanced
			@Since: 2.14
			Set the Jy/K conversion factor to X. This allows CRUSH
			to calculate a data conversion to 'kelvin' units if
			'jansky' is also defined. Alternatively the conversion
			to kelvins can be specified directly via the 'kelvin'
			key.
			@See: 'kelvin', 'jansky'

:: kelvin=X		@Advanced
			@Since: 2.14
			Set the conversion to 'kelvin' units (or more precisely
			to 'K/beam' units). X defines the equivalent value of
			1 K/beam expressed in the native data units.
			@See: 'dataunit', 'jansky', 'K2Jy'

:: list.divisions	@Since: 2.16
			@Advanced
			Print out the names of all available pixel divisions
			which can be decorrelated.
			@See: 'correlated.<?>', 'write.coupling', 
				'list.response'

:: list.response	@Since: 2.16
			@Advanced
			Print out the names of all available response 
			modalities (to known signals).
			@See: 'correlated.<?>', 'write.coupling'
				'list.divisions'


:: .lock[=value]	@Since: 2.31
			Set a persistent option value, that cannot be
			changed, cleared, or blacklisted later (e.g. by 
			conditionally activated settings). Users may use locks
			to ensure that their manually set reduction options
			are applied, and never overrriden. For the lock to
			take effect, the option must not be blacklisted or
			locked to a different value before.
			Without the optional value argument, the lock will
			make the current setting (whatever it is at the time
			the lock is invoked) persistent. E.g.:

			   stability=5.0
			   [...]

			   > crush [...] -stability.lock [...]

			If the optional <value> argument is given, then the
			<option> will be set to that value before the <lock>
			is created:

			   > crush [...] -stability.lock=5.0
			
			will lock 'stability' to 5.0. To release a lock, use
			the '<option>.unlock' directive. To re-lock to a new
			value (same unlock and lock again) use 
			'<option>.unlock'.	

			@See: '.unlock', '.relock', 'blacklist'


:: log			@Advanced
			@Since: 2.03
			Log the scans after the reduction. (Similar logging
			is available without reducing at all via the 'obslog'
			key). You can control what quantities are logged and
			in what format via the 'log.format' key. Please refer
			to the README for details on how the logging works and
			what you many log and how.
			@See: 'obslog', 'log.file', 'log.format', 
			      'log.conflict'

:: log.conflict=<value>		@Expert
				@Since:2.03	
			Since log files are locked to their format, a changing
			for format without specifying a new log file will 
			cause a conflict. Use this key to determine how such
			conflicts are resolved. The following values are
			permitted:

			   overwrite	Delete the previous log file, and 
					create a new one with the same name
					using the new format.

			   version	Try find an alternative version of the
					log file (with .1, .2 ... extension
					attached to the file name) in the new
					format, or create a new such version.
			
			The default behaviour is to assume versioning, in order
			to preserve prior logs.
			@See: 'log.file'

:: log.file=<path>	@Advanced
			@Since:2.03
			Set the file to which reductions will be logged. You
			can use the usual path specifications of CRUSH, 
			including shorthands (such as '~') and environment
			variables (such as {$HOME}). The actual log file used
			may be a sub-version of the specified file (with
			.1, .2 ... extension added) if the conflict policy
			set by 'log.conflict' is to use versioning.
			@See: 'log', 'log.format', 'log.conflict'

:: log.format=		@Expert
			@Since: 2.03
			Specify the format of the log file. You can control 
			what quantities are logged and how they should appear.
			Please refer to the README for more details on the
			available options
			@See: 'log', 'log.file', 'log.format'

:: los			@Instrument: HAwC+
			@Since: 2.41
			@Expert
			@Alias: 'correlated.los'
			Remove correlations with the second-derivative to the
			telescope line-of-sight (LOS) angle. It's a good proxy
			for removing pitch-type acceleration response from the
			detector timestreams.
			@See: 'correlated.<?>'

:: maitau.225GHz=<path>		@Advanced
				@Instrument: SHARC-2
				@Since: 2.41
			Specify the file with the 225GHz MaiTau coefficients.
			@See: 'tau.225GHz'				
		
:: maitau.350um=<path>		@Advanced
				@Instrument: SHARC-2
				@Since: 2.41
			Specify the file with the 350um MaiTau coefficients.
			@See: 'tau.350um'				
		
:: maitau.fallback=<type>	@Instrument: SHARC-2
				@Advanced
			Define which tau value to use in case the MaiTau lookup
			fails. The possible values are:

			   direct 	  Calculate tau from the total-power
			       		  loading of the detectors

			   225GHz	  Use the 225GHz tipper value.

			   350um	  Use the 350um tipper value.

			   pwv		  Use precipitable water vapor.

			   sharc2	  Use the value specified by tau.sharc2

			Other than the 'direct' flag, the values may be 
			specified with the corresponding tau settings.
			@See: 'maitau.225GHz', maitau.350um', 'tau.225GHz', 
			'tau.350um', 'tau.sharc2'

:: mappingfraction=X   	@Advanced
			Specify a minimum fraction of pixels in the array
			that have to remain unflagged for creating a map
			from the scan. If too many pixels are flagged in the
			reduction, it may be a sign of bigger problems, 
			questioning the reliability of the scan data. It is best
			to skip over problematic scans in order to minimize 
			their impact on the mapping.
			@See: 'mappingpixels'

:: mappingpixels=N	@Advanced
			Specify a minimum number of pixel, which have to
			be unflagged by the reduction in order for the scan to
			contribute to the mapping step
			@See: 'mappingfraction'

:: map.size=X,Y		@Advanced
			Explicitly set the size of the mapped are, centered on 
			the source to and X by Y arcseconds rectangle. Normally,
			the map size is automatically calculated to contain all
			of the data. One may want to restrict mapping to smaller
			regions (outside of which, there should be no bright
			sinals). The letter 'x' may also be used instead of the
			comma to separate the dimensions. E.g.:

			   map.size=300x200

			will restrict mapping to a 300" by 200" are (in the 
			chosen coordinate system of the mapping), centered on
			the nominal source coordinates.
			@See: 'system'

:: mask=<path>		@Since: 2.33
			@Advanced
			Flag out data around the specified catalog of sources.
			The input file defined by <path> is the usual CRUSH
			catalog format. Any samples falling within the regions
			defined in the mask will be flagged and ignored in the
			reduction. This is useful, for example, to look at
			faint emission around a bright source.
			@See: 'sources'

:: mjd.[...]		@Advanced
			Specify settings that are conditionally activated if and
			when the MJD of the scan falls within the specified 
			range inside the square brackets. Wildcards '*' can be 
			used to indicate open ended ranges. E.g.:

			       mjd.[*-54230.25] jansky=5.0

			specifies that up until 6:00 UT on 10.05.2007, the 
			conversion factor of 5.0 data units per Jy should be
			used.
			@See: 'date.[...]', 'serial.[...]'

:: moving		@Since: 2.15
			Specify, explicitly, that the object is moving in the
			celestial frame (such as solar system objects, like
			planets, asteroids, comets and moons). This way, data
			will be properly aligned on the coordinates of the 
			first scan. If the data headers are correctly set up
			(and interpreted by crush) moving objects can be auto
			detected. This option is there, in case, things do not
			work as expected (e.g. if you notice that your solar
			system object smears or moves across the image with the
			default reduction.
			Currently, the option forces equatorial coordinates.
			The options is also aliased as 'planetary', to keep
			compatibility with earlier releases.
			@See: 'system'

:: multibeam		@Alias -> source.type=multibeam

:: mux			@Alias -> correlated.mux
			@Instrument: SHARC-2, GISMO, SCUBA-2
			@Advanced
			Decorrelate on MUXes, or set options for it.
			@See: 'correlated.<?>'

:: name=		Specify the output image file name, relative to the
			directory specified by 'outpath'. When not given
			minicrush will chose a file name based on the source
			name and scan number(s), which is either

				<sourcename>.<scanno>.fits

			or
	
				<sourcename>.<firstscan>-<lastscan>.fits

			For mapping. Other source model types (e.g. skydips
			or pixel maps) may have different default naming 
			conventions.
			@See: 'outpath'

:: ndf2fits=<path>	@Instrument: SCUBA-2
			@Since: 2.01-1
			SCUBA-2 data is released in a proprietary SDF format,
			which is not well documented for direct use. Instead,
			the StarLink software suite provides utilities for
			manipulating such files. Among these it provides a
			conversion utility 'ndf2fits' that can translate SDF
			files into FITS files readable by CRUSH. You can do 
			the conversion yourself using the 'proexts' option.
			Or, you can let CRUSH convert the input files on-the-
			fly, as necessary. This option serves to specify the
			full path to the ndf2fits utility, including the
			executable name. E.g.:
			
			  ndf2fits=/usr/local/starlink/convert/ndf2fits

			Clearly, you will need a functional installation
			of the Starlink software or, at minimumm it conversion
			package, for this option to work.

:: nefd.map		@Since: 2.14
			@Expert
			Try use the apparent map noise (if available, e.g. via
			'weighting.scans') to refine the reported NEFD estimate
			(e.g. for loggig via 'log'). Else, the NEFD estimate
			will be based on the timestream noise alone. 

:: nochopper		@Instrument: SHARC-2, MAKO
			@Advanced
			@Since:2.16-1
			Ignore the chopper position signal (if at all present).

:: noiseclip=X		Flag (clip) map pixel with a noise level that is more
			than X times higher than the deepest covered parts
			of the map.
			@See: 'exposureclip', 'clip'

:: nogaps		@Instrument: SHARC-2
			@Advanced
			Terminate the reading of the data at the first 
			gap. During the early SHARC-2 runs when JSharc was used 
			for the acquisition of the data, there was an 
			occasional damaging timing bug resultuing from the 
			wraparound of an internal buffer. The bug manifested in
			a sudden jump in the timestamps, making it relatively 
			easy to diagnose if this happened during the scan.

:: noresistors		@Instrument: LABOCA
			@Expert
			Do not use the resistor channels in the decorrelation of
			electrinic signals, such as 'boxes', 'cables' and 
			'amps'. In LABOCA several of the readout channels are 
			connected not to light-sensitive detectors, but to 
			fixed resistors. While these are not sensitive to 
			radiation or temperature the channels will still be 
			subject to electronic pickup. Therefore, the default is
			to use these channels when decorrelating signals, which
			are thought to originate within the electronics. This 
			option can be used to overrride this behavior, and 
			restrict all decorrelation steps to detector channels 
			only.
			@See: 'boxes', 'cables', 'amps'
		
:: noslim		@Expert
			After reading the scans, CRUSH will discard data from
			from channels flagged with a  harware problem (any bit 
			in 0xFF), to free up memory, and to speed up the 
			reduction. This option overrides this behaviour, and 
			retains all channels for the reduction, whether these 
			are used or not.

:: notch		@Since: 2.30
			@Expert
			Enable notch filtering the raw detector timestreams
			before further initial processing (e.g. downsampling).
			The sub-options 'frequencies', 'harmonics' and 'width'
			are used to customize the notch filter response.

:: notch.frequencies=<list>	@Since: 2.30
				@Expert
			A comma-separated list of frequencies (Hz) to notch
			out from the raw detector timestreams.
			@See: 'notch.width', 'notch.harmonics'

:: notch.harmonics=N	@Since: 2.30
			@Expert
			Specify that the notch filter should also notch out
			N harmonics of the specified frequencies. (If not
			set, only the list of frequencies are notched, i.e.
			same as 'harmonics=1'.). E.g.

			  notch.harmonics=2

			Will notch out the list of frequencies set by 
			'notch.frequencies' (fundamentals) as well as their
			second harmonics.
			@See: 'notch.frequencies', 'notch.width'

:: notch.width=X	@Since: 2.30
			@expert
			Set the frequency width (Hz) of the notch filter
			response.
			@See: 'notch.frequencies'

:: object=<name>	@Instrument: GISMO
			Can be used to help locate GISMO data with scan numbers
			when used together with the 'datapath' and 'date' 
			options.
			E.g.:
			
			  > crush [...] -datapath=. -object=Mars \
			    -date=2010-04-15 12-14

		 	Will reduce Mars scans 12 to 14 from Apr 15, 2010. The
			object name is case-sensitive!
			@See: 'datapath', 'date'


:: object.[...]		@Since:2.05
			@Advanced
			Allows you to set conditionals based on object names.
			All source names that begin with the specified string
			(case insensitive!) will satisfy the condition. Thus,
			the SHARC-2 setting:

			   object.[PNT_] point

			will automatically perform a pointing fit (see 'point'
			option) at the end of the reduction for all sources
			whose catalog names begin with 'PNT_', such as 
			'PNT_3C345'.
			@See: 'point'

:: obslog		@Advanced
			@Since: 2.03
			Log the scans immediately after reading, and without
			reducing them at all. (Similar logging is available 
			post reduction via the 'log' key). Please refer to the 
			README for details on how the logging works and what 
			you may log and how.
			@See: 'log', 'obslog.file', 'obslog.format', 
			      'obslog.conflict'

:: obslog.conflict=<value>	@Expert
				@Since:2.03	
			Since log files are locked to their format, a changing
			for format without specifying a new log file will 
			cause a conflict. Use this key to determine how such
			conflicts are resolved. Please refer to 'log.conflict'
			for details.
			@See: 'log.conflict', 'obslog.file'

:: obslog.file=<path>	@Advanced
			@Since:2.03
			Set the file to which scans will be logged. Refer to
			'log.file' for details.
			@See: 'log.file', 'obslog.format', 'obslog.conflict'

:: obslog.format=	@Expert
			@Since: 2.03
			Specify the format of the obslog file. You can control 
			what quantities are logged and how they should appear.
			Please refer to the README for more details on the
			available options
			@See: 'obslog', 'obslog.file', 'obslog.format'

:: obstime.[]		@Advanced
			@Since: 2.34
			Configure settings based on the total observing time
			of all input scans. The condition inside the brackets
			is a minimum or maximum obsercing time in seconds. E.g.
		
			  obstime.[<60]
			  obstime.[>60]

			The first activates for datasets longer than 1 minute,
			the second for datasets shorter than a minute. Nesting
			obstime conditions is possible with some limitations.
			It is evaluated only once, after all scans have been
			read. Thus, the condition will have no effect if 
			activated later (e.g. if nested inside an iteration.[]
			condition.).	

:: offset.*		@Instrument: SCUBA-2, HAWC+, HIRMES
			Specify subarray offsets. See the instrument README
			docs for specifics.
			@See: 'rotation.*'

:: offsets		@Advanced
			Remove the residual DC offsets from the bolometer 
			signals (ignored when 'drifts' below is also 
			specified.)
			@See: 'drifts'

:: ordering=a,b,c	@Advanced
			Specify the order of pipeline elements as a comma
			separated list of keys.
			@See: 'offsets', 'drifts', 'weighting', 'despike'
			      'source', 'correlated.<?>', 'whiten',
			      'time-weighting'

:: organization         @Telescope: SOFIA
			@Since: 2.42
                        Specify the organization at which CRUSH is being used
                        for reducing data. The value of this option is stored
                        directly in the FITS ORIGIN header key as required by
                        the DCS. If you want the ORIGIN key to be set properly
                        you might consider adding the organization option to
                        `~/.crush2/sofia/default.cfg`, e.g. as:

                          organization SOFIA Science and Mission Ops

:: outpath=<path>	Specify the output path, where all CRUSH output will be 
			written (including maps etc.). Path names follow the
			usual rules (See 'Basic Configuration' section in the
			README), and can use '~' to refer to the home 
			directories or to environment variables in {} brackets 
			with a $ sign.
			E.g.

				outpath={$HOME}/images

			in UNIX specifies the 'images' subdirectory inside a
			user's home.

:: outpath.create	@Since: 2.13
			When specified, the output path will be automatically
			created as necessary. If not set, CRUSH will exit
			with an error if the output path does not exist.
			@See: 'outpath'

:: parallel=<mode>	@Since:2.30
			@Advanced
			Set the parallel processing mode. The argument is one
			of:

			   scans    process scans in parallel
			   ops	    process each scan with parallel threads
			   hybrid   process as many scans in parallel as
			            possible, each with an optimal number of
				    threads.

			The default mode is 'hybrid'. The 'scans' is what 
			parallelization used to be before 2.30.
			@See: 'threads', 'idle'


:: pcenter=row,col	@Instrument: SHARC-2, GISMO, MAKO
			@Advanced
			Defines the pointing center used, in terms of the
			instrument pixel row and colum coordinates. Pixel 1,1
			designates the top-left corner of the array in 
			horizontal (AZ/EL) or equivalent Nasmyth coordinates. 
			Columns increase to the right, while row numbers 
			increase downward. Thus, the center of the 
			SHARC-2 array is 6.5,16.5, while the center of GISMO is 
			8.5,4.5. The 'pcenter' option is not used if the pixel 
			positions are loaded from an RCP data file, instead of 
			being calculated (since a rectangular grid can no 
			longer be assumed).
			@See: 'rcp', 'rcenter', 'pixelsize', 'rotate'

:: peakflux		@Instrument: HAWC+
			@Since: 2.41
			Switch to peak-flux calibration instead of the default
			aperture flux calibration. Recommended for point
			sources only.

:: perimeter=N		@Expert
			@Since: 2.30
			To speed up the sizing of the output image for large
			arrays (e.g. SCUBA-2 or HAWC+) do not use the positions
			of each and every pixel. Instead, identify a set of
			pixels that define an array perimeter from N sections
			around the centroid of the array. N values up to a few
			hundred should be fail-safe for most typical array
			layouts, even when these have lots of pixels.

			@Since: 2.32
			The value 'auto' will use an optimal number of sections
			for the perimeter calculation.

:: phases		@Expert
			@Since: 2.02
			Decorrelate also the phase data (e.g. for chopped 
			observations) for all correlated modes. Alternatively
			phase decorrelation can be turned on individually for
			modalities using the 'correlated.<?>.phases' options.
			@See: 'correlated.<?>.phases'
		
:: phases.estimator=<value>	@Expert
				@Since: 2.04
			Allows to override the global estimator setting for
			the phases (e.g. chopper phases). The <value> can be
			either 'median' or 'maximum-likelihood' all other
			values default to 'maximum-likelihood'. When not set
			the global 'estimator' setting will be used for the
			phases also.
			@See: 'estimator'

:: phasegains		@Expert
			@Since: 2.04
			Use the information in the phases to calculate gains
			for all correlated modes. (The default is to use the
			fast samples for calculating gains). Alternatively you
			can set this property separately for each correlated
			modality.
			@See: 'correlated.<?>.phasegains'

:: pins			@Alias -> correlated.pins
			@Instrument: GISMO, SCUBA-2
			@Advanced
			Decorrelate on readout address lines (across the MUXes)
			or set options for it.
			@See: 'correlated.<?>', 'pins.group', 'mux'

:: pins.group=N		@Instrument: GISMO
			@Expert
			Based on the 'pins' alias for GISMO, it defines a 
			grouping of N neighbouring address lines. For each MUX,
			there are 32 address lines, which are read out 
			sequentially in the time-domain multiplexing scheme. 
			Thus,

			   pins.group=4
			   
			will group the address lines 1-4, 5-8, ..., 29-32 
			together across all MUXes, thus increasing the number 
			of channels in each group. The decorrelation of address
			lines using the 'pins' option will take place on these 
			groups.
			@See: 'pins', 'mux'

:: pixeldata=<filename>	@Expert
			Specifies a pixel data file, providing initial
			gains, weights and flags for the detectors,
			and possible other information as well depending on the
			specific instrument. Such files can be produced via the
			'write.pixeldata' option (in addition to which you
			may want to specify 'forget=pixeldata' s.t. flags are
			determined without prior bias).
			@See: 'gainnoise', 'uniform', 'flag', 'blind'

:: pixelmap		@Since: 2.42
			(Used to be 'beammap')
			Effectively the same as 'source.type=pixelmap', which 
                        is invoked by a condition, not an alias because 
                        aliasing would interfere with the similarly named 
			'pixelmap.process' and 'pixelmap.writemaps' options.
			Used for reducing pixel map data. Instead of making a 
			single map from all pixels, separate maps are created 
			for each pixel (Note, this can chew up some memory if 
			you have a lot of pixels). At the end of the reduction 
			CRUSH determines the actual pixel offsets in the focal 
			plane.
			@See: 'source.type', 'map', 'skydip', 'grid'
	
:: pixelmap.process	@Advanced
			(Used to be 'beammap.process')
			Specify that pixel maps should undergo the same
			post-processing steps (e.g. smoothing, clipping
			filtering, etc.) that are used for regular map-making.
			When the option is not set, pixel maps are used in 
                        their raw maximum-likelihood forms.
			@See: 'pixelmap', 'pixelmap.writemaps'

:: pixelmap.writemaps	Pixel maps normally only produce the pixel position 
			information as output. Use this option if you want 
                        CRUSH to write individual pixel maps as well, so you  
                        can peek at these yourself.
			@See: 'pixelmap', pixelmap.process'
			
:: pixelsize=X,Y	@Instrument: SHARC-2, GISMO, P-ArTeMiS, MAKO
			@Expert
			Specify the size of rectangular pixels in a grid. This
			is used for calculating pixel positions on a rectangular
			grid. The information is ignored when positions are
			loaded from an RCP data file (as a regular grid can no 
			nonger be assumed).
			@See: 'rcp', 'pcenter', 'rcenter'

:: planetary		@Since: 2.11
			@Deprecated: 2.15
			@Alias -> moving

:: platescale=X         @Instrument: HIRMES
                        @Expert
                        @Since: 2.42
                        Override the plate scale recorded in the FITS, and
                        set it manually to X arcsec/mm.
                        @See: 'pixelsize'

:: point		@Since: 2.00-b4
			This is a convenience key for triggering settings for
			reducing pointing scans. Currently, it invokes
			'iteration.[last] pointing=suggest', i.e. suggesting 
			pointing corrections in the last iteration.
			@See: 'pointing', 'pointing.method', 'fazo', 'fzao'

:: pointing=<value>	@Since: 2.00-b4
			Specify pointing corrections, or the way these
			should be derived. The following values are 
			accepted:			 
	
			   x,y		Specify relative pointing offsets as 
					comma-separated valutes (in arcseconds) 
					in the system of the telescope mount. 
					I.e., these should be horizontal
					offsets for ground-based telescopes 
					with an Alt/AZ mount. 
					Some instruments may allow more ways
					to specify pointing corrections (E.g.
					'fazo' and 'fzao' for SHARC-2).

			   suggest	Suggest pointing offsets (at the end
					of the reduction) from the scan itself.
					This is only suitable when reducing 
					compact pointing sources with 
					sufficient S/N to be clearly visible in
					single scans.

			@See: 'point', 'fazo', 'fzao'

:: pointing.exposureclip=X	@Since: 2.04
				@Expert
			Clip away the underexposed part of the map, below a 
			relative exposure X times the most exposed part of the 
			map. The option works similar to the 'exposureclip' 
			option, but applies only to the map used for deriving 
			the pointing internally.
			@See: 'exposureclip'	

:: pointing.method=<value>	@Since: 2.00-b4
				@Expert		
			Specify the method used for obtaining positions of 
			pointing sources. Currently 'centroid' (default) and 
			'peak' are supported. This option also controls how 
			pixel position information (RCP) is calculated for 
			'pixelmap' reductions.
			@See: 'point', 'pixelmap'

:: pointing.model=<name>	@Advanced
				@Instrument: GISMO
				@Since: 2.04
			Use a pointing model to derive and apply pointing 
			corrections automatically. The argument is the
			name of the file containing the pointing constants. The
			file is simply an ASCII file, with separate lines 
			containing the pointing constants and their incremental
			values. E.g., the pointing model file derived for
			2011 Apr 13 contains the entries:

				P4 = 22.54
				P5 = 17.17
				P9 = -11.56
				P10 = -38.59
				P11 = 2.60

			You can still apply a incremental offset on top of this
			model, using the 'pointing' key the usual way.
			By default, the pointing model contains aggregated 
			constants, which are compared to the telescope model
			to calculate appropriate corrections. However, it is
			also possible to supply incremental constants if the
			'pointing.model.incremental' option is also set.
			@See: 'pointing', 'pointing.model.incremental'
			      'pointing.model.static', 'pointing.table'

:: pointing.radius=X	@Since:2.41
			@Advanced
			Restrict the pointing fit to a circular area, with
			radius X (arcsec), around the nominal map center. It 
			may be useful for deriving ponting in a crowded' field.
			@See: 'pointing.suggest'

:: pointing.model.incremental	@Instrument: GISMO
				@Since: 2.04-2
				@Advanced
			Specify the the pointing model supplied via 'pointing
			model is an incremental model on top of whatever model
			was used during the observations.
			@See: 'pointing.model'

:: pointing.model.static	@Instrument: GISMO
				@Since: 2.04-2
				@Expert
			Use the static terms only of the supplied pointing
			model. By default the GISMO model can have time variant
			coefficients defined also. When this option is set, the
			time variability will be ignored, and only the static
			values are used.
			@See: 'pointing.model'

:: pointing.significance=X	@Since: 2.00-0
				@Expert
			Set the significance (S/N) level required for pointing
			sources to provide a valid pointing result. If the
			option is not set, a value of 5.0 is assumed.

:: pointing.suggest	@Since:2.40
			Fit pointing for each input scan at the end of the
			reduction. It can also be triggered by the 'point'
			shorthand (alias), and may be enabled by default for
			certain type of scans, depending on the instrument.
			E.g. for SHARC-2, pointing fits are enabled for sources
			whose names begin with 'PNT_' or 'CAL_'; or for HAWC+
			pointing fits are automatically enabled for short, 
			single-scan reductions.
			@See: 'pointing.significance', 'pointing.radius', 
			      'pointing.exposureclip', 'pointing.method'

:: pointing.table=<name>	@Advanced
				@Instrumment: GISMO
				@Since: 2.04
			Use a pointing table (obtained via the 'log' option) to
			derive residual pointing corrections, on top of the
			pointing model. You can still use 'pointing' to add yet
			another increment. For the residual correction to
			work, the log file must contain the columns 'id', 'AZ',
			'EL', 'pnt.X', 'pnt.Y', 'src.peak', 'src.dpeak', and
			'src.FWHM'. The routine will weight pointing data by
			distance to source, and by distance in time of 
			observation. When using this option, you should make
			sure to remove or comment out any entries with 
			unreliable pointing results.
			@See: 'pointing', 'pointing.model'

:: pointing.tolerance=X		@Since: 2.15
				@Expert
			Control how close (relative to beam FWHM) the 
			telescope pointing must be to its target position for 
			determining the photometry. A distance of 1/5 beams
			can result in 10% degradation on the boundaries, while 
			the signal would degrade by 25% at 1/3 beams distance.
			The setting has no effect outside of photometry
			reductions.
			@See: 'phases', 'chopped'

:: pol			@Alias --> 'source.polar'
			@Since: 2.10

:: poll[=<key>]		Whenever unsure what options are set at any given stage,
			you can poll the settings. Without an additional 
			argument it will list all currently defined setting to 
			the standard output. When an argument is specified it 
			will list the configuration settings that start with 
			the specified string. E.g.

			    > crush [...] -poll=despike
	
			will list all despiking options (e.g. all settings 
			under the 'despike', 'despike2', and 'despike3'
 			branches) that have been defined prior to the
 			invokation of the '-poll' command.
			Due to the hierarchical nature of the configurations
			you can also selectively poll settings under subtrees
			of the configuration. E.g.:

			   > crush [...] -source.poll

			Will lists all source model related settings stored
			under the 'source' subtree.
			@See: 'conditions', 'blacklist'

:: positions.smooth=X	@Expert
			Specify that the telescope encoder data should be
			smoothed with a time window X seconds wide, in 
			order to minimize the effects on encoder noise on the
			calculation of scanning speeds and accelerations, based
			on which data may be discarded, and optimal downsampling
			rates are determined.
			@See: 'aclip', 'vclip', 'downsample'

:: project=<id>    	@Telescope: APEX
			Some instruments (e.g. APEX bolometers) may require a 
			project ID to be set in order to locate scans by serial 
			number. Use capitalized form when defining APEX 
			projects. E.g.,

                              project T-79.F-0002-2007


:: projection=		Choose a map projection to use. The following 
			projections are supported:

				SFL  --  Sanson-Flamsteed
				SIN  --  Slant Orthographic
				TAN  --  Gnomonic
				ZEA  --  Zenithal Equal Area
				MER  --  Mercator
				CAR  --  Plate-Carree
				AIT  --  Hammer-Aitoff
				GLS  --  Global Sinusoidal
				STG  --  Stereographic		(since 2.16)
				ARC  --  Zenithal Equidistant	(since 2.16)

			@See: 'system', 'grid', 'mapsize'

:: propertry.[]		@Since: 2.34
			@Advanced
			Set options conditionally based on the values of
			Java properties. The syntax is similar to the 'env.[]'
			option (which sets CRUSH options conditionally based
			on the shell environment). Inside the brackets, two
			types of conditions may exists:
			
			  1. Match the value of a system property. E.g.:

			       property.[user.name?bar]

			     is true if 'user.name' is 'bar'.

			  2. Match to any other value. E.g.:

			       property.[user.name?!bar]

			     is true, if 'user.name' is anything but 'bar'.

			@See: 'env.[]'

:: purify		@Instrument: PolKa
			@Advanced
			@Since: 2.11
			Really a generic option for getting rid of unwanted
			signals before the mapping step. The exact action may 
			be different from one instrument to another. For now, 
			only PolKa uses this option for removing the total-
			power modulation before producing the Q and U maps. The
			method uses a template of the modulation as a function
			of the phase. It should work perfectly, if the 
			waveplate angles are accurately known. However, FFT
			filtering (via 'filter.hwp') is more suited for
			uncertainties in the waveplate angles.
			@See: 'filter.hwp'

:: pwv41k=X		@Telescope: SOFIA
			@Expert
			@Since: 2.34
			Set the typical PWV value to X microns at 41 kilofeet
			altitude.
			@See: 'pwvmodel', 'pwvscale'

:: pwvmodel		@Telescope: SOFIA
			@Expert
			@Since: 2.34
			Estimate a typical PWV value (for opacity correction)
			based on altitude alone.
			@See: 'pwv41k', 'pwvscale'

:: pwvscale=X		@Telescope: SOFIA
			@Expert
			@Since: 2.34
			The typical water vapor scale height (kft) around 41 
			kilofeet altitude.
			@See: 'pwvmodel', 'pwv41k'

:: quiet		@Since: 2.33
			@Advanced
			Suppress most console output, but keep reporting any
			warnings and errors, as well as results and 
			notifications.
			@See: 'veryquiet'

:: radec		@Alias -> system=equatorial
			Reduce using equatorial coordinates (for mapping).
			(Default)
			@See: 'system', 'altaz'

:: range=min:max	@Expert
			@Since: 2.03
			Set the acceptable range of data (in the units it is
			stored). Values outside of thi range will be flagged,
			and pixels that are consistent offenders will be
			removed from the reduction (as set by 
			'range.flagfraction').
			@See: 'dataunit', 'range.flagfraction', 'range.auto'	

:: range.auto		@Expert
			@Instrument: LABOCA
			@Since: 2.03
			Set the ADC range automatically using the actual 
			backend gain setting
			@See: 'range'

:: range.flagfraction=X		@Expert
				@Since: 2.03
			Specify the maximum fraction of samples for which a
			channel can be out of range (as set by 'range') before
			that channel is flagged and removed from the reduction.
			@See: 'range'

:: rcenter=dX,dY	@Instrument: SHARC-2, MAKO
			@Expert
			Specify a rotation center, in the coordinate system of
			the array (AZ,EL or Nasmyth coordinates). Works 
			similarly to 'pcenter'
			@See: 'pcenter'

:: rcp=<filename>	@Advanced
			Use the RCP file from <filename>. The usual rules of
			path specification apply (see the 'Basic Configuration' 
			section of the README.). The file should conform to the
			standard IRAM or APEX RCP specs containing the 
			information in ASCII columns. RCP files can be produced 
			by the 'pixelmap' option, from scans, when the 
			observation moves a bright source over all pixels.
			For rectangular arrays, pixel positions can also be 
			calculated on a regular grid using 'pixelsize' and 
			'pcenter'
			@See: 'pixelmap', 'pixelsize', 'pcenter' 

:: rcp.center=x,y	@Advanced
			Define the center RCP position at x,y in arcseconds.
			Centering takes place immediately after the parsing
			of RCP data.
			@See: 'rcp'

:: rcp.gains		@Advanced
			Calculate coupling efficiencies using gains from the 
			RCP files. Otherwise uniform coupling is assumed with
			sky noise gains from the 'pixeldata' file.
			@See: 'rcp'

:: rcp.rotate=X		@Advanced
			Rotate the RCP positions by X degrees (counter 
			clockwise). Rotations take place after centering (if
			specified).
			@See: 'rcp'

:: rcp.zoom=X		@Advanced
			Zoom (rescale) the RCP position data by the scaling
			factor X. Rescaling takes place after the centering
			(if defined).	
			@See: 'rcp'

:: read=<list>		Read the scans in the list. The list can be a comma, or
			space-separated list of arguments, which can be contain
			the following types of arguments:
			
			  <filename>	Read the scan data from <filename>, 
			  		which can be either a fully specified 
					path, or relative to 'datapath'. 

			  N		Read scan number N. May need additional
			  		options such as 'project' (APEX) or
					'date' and 'object' (GISMO) to be set in
					order to locate the data in a filesystem
					hierarchy.

			  from-to	A hyphen '-' separated range of scan 
			  		numbers (inclusive). Same considerations
					apply as above.

			In all cases, the 'read' key can be omitted on the 
			command  line, where it suffices to list the arguments 
			with white spaces, without any option key. E.g.:

			 > crush [...] myscan.fits 11564 12067-12071

			@See: 'datapath', @APEX:'project', @GISMO:'date',
			      @GISMO:'object'

:: recall=<option>	Undoes 'forget', and reinstates the <option> to its 
			old value.
			@See: 'forget'	


:: regrid=X		@Advanced
			@Since: 2.30
			Regrid the final map to a different grid than what was
			used during the reduction. The argument is the final
			image pixel size in arcsec. E.g.

			  > crush [...] -regrid=1.0 [...]

			to cast the final image onto a 1" pixel grid.		
			@See: 'grid'

:: .relock=value	@Since: 2.31
			Create a new persistent setting for the option, even if
			the option was locked to another setting previously
			Thus, for example:
			
			  stability.relock=10.0

			is effectively a shorthand for:

			  stability.unlock		
			  stability.lock=10.0		
			   			
			@See: '.lock', '.unlock', 'blacklist'

:: remove=<option>	Similar to 'forget', but removes the entire branch. 
			Thus '-remove=despike' unsets:

				despike
				despike.level
				despike.method
				despike.flagfraction
				...

			Branches can be reinstated to their prior state using 
			the 'restore' command.
			@See: 'forget', 'restore'

:: reservecpus=N	@Alias: 'idle'

:: resolution=X		@Advanced
			Define the resolution of the instrument. For single-
			color imaging arrays, this is equivalent to 'beam', 
			with X specifying the instrument's main beam FWHM in 
			arcsec. Other instruments (like heterodyne receivers) 
			may interpret 'resolution' differently.
			@See: 'beam'

:: response=<filename>	@Instrument: SHARC-2
			@Expert
			Specify the <filename> containing the pixel 
			loading information, based on which in-band 
			line-of-sight opacities may be calculated.
			@See: 'response.calc', 'tau', 'tau.<?>'

:: response.calc	@Instrument: SHARC-2
			@Expert
			Allows the recalculation of pixel responses, based on an
			initial 'response' provided in a file, and a 'tau' 
			value. Scans on very faint or deep-field sources are 
			most suited for such recalculations. Use this option 
			only if you really understand what it is meant to do.
			@See: 'response', 'tau', 'tau.<?>'

:: restore=<option>	Undoes the 'remove' option, reinstating the <option> 
			tree to its prior state.
			@See: 'remove'

:: roll			@Instrument: HAWC+
			@Since: 2.41
			@Expert
			@Alias: 'correlated.roll'
			Remove correlations with the second-derivative of the
			aircraft roll angle (roll-type accelerations).
			@See: 'correlated.<?>'

:: rot0			@Instrument: SHARC-2, MAKO
			@Expert
			Specifies the reference (zero point) of the rotator (if
			available). This option applies only for the early 
			SHARC-2 runs, when the instrument was still mounted on 
			the Cassdegrain platform. The values should be correcly
			configured in the default SHARC-2 configuration 
			('config/sharc2/default.cfg'), and there should be no 
			reason for the user to change these settings...
			@See: 'rotation'

:: rotation		@Advanced
			Define the instrument rotation (in degrees) if
			applicable.	

:: rotation.*		@Instrument: SCUBA-2, HAWC+, HIRMES
			Specify subarray offsets. See the instrument README 
			docs for specifics.
			@See: 'offset.*' 

:: rounds=N		@Advanced
			Iterate N times. You may want to increase the number
			of default iterations either to recover more extended
			emission (e.g. when 'extended' is set), or to go
			deeper (esp. when the 'faint' or 'deep' options are
			used).
			@See: 'iteration.[?]', 'extended', 'faint', 'deep'

:: rows			@Alias: -> correlated.rows
			@Instrument: SHARC-2, P-ArTeMiS, HAWC+, SCUBA-2
			@Advanced
			Decorrelate on detector rows, or set options for it.
			@See: 'correlated.<?>'

:: rtoc			@Expert
			@Instrument: HAWC+
			@Since: 2.33
			Instruct crush to reference maps to Real-Time Object 
			Coordinates (RTOC) for sidereal and non-sidereal
			sources alike. Normally, sidereal object coordinates
			are determined via the header keywords OBSRA/OBSDEC or
			OBJRA/OBJDEC. However, these were not always filled
			correctly during the 2016 October flights, so this
			option provides a workaround for those scans.

:: scale=<arg>		Set the calibration scaling of the data. The option
			can take as argument, either:

			    X	    	    An explicit scaling value X, by 
			    		    which the entire scan data is 
					    scaled. E.g.
					    
					      scale=0.92


			    <filename>	    the name of a calibration file, 
			    		    which among other things, contains 
					    the ISO time-stamp and the 
					    corresponding calibration values 
					    for each scan. The filenames follow
					    the usual path conventions of CRUSH
					    and may contain references to 
					    environment variables enclosed in 
					    {} brackets. E.g.:

					      scale={$HOME]}/laboca/scaling.dat

			Note, that not all instruments support the <filename>
			argument!

			@See: 'scale.window', 'tau', 'gain', 'invert', 
			      'jackknife'

:: scale.window=X	@Expert
			@Instrument: LABOCA, SABOCA
			@Since: 2.13
			Set the 1-sigma Gaussian weighting window (in hours)
			for deriving local weighted average scaling values from 
			a table of calibrattion measurements.
			@See: 'scale', 'tau.window'

:: scanmaps		@Advanced
			When specified, a map will be written for each scan
			(every time it is solved), under the name 
			'scan-<scannumber>.fits' in the usual output path.
			Best to use as:
			     
			     final:scanmaps
 			
			to avoid the unnecessary writing of scan maps for every
			iteration (unless you really want that to be the case).
			@See: 'final', 'source'

:: scramble		Make a map with inverted scanning offsets. Under the
			typical scanning patterns, this will not produce a
			coherent source. Therefore it is a good method for
			checking on the noise properties of deep maps. The 
			method essentially smears the source flux all over the 
			map. While not as good as 'jackknife' for producing pure
			noise maps, 'jackknife' requires a large number of scans
			for robust results (because of the random inversion),
			whereas 'scramble' can be used also for few, or even 
			single scans to nearly the same effect.
			@See: 'jackknife'

:: segment=X		@Expert
			@Since: 2.30
			Break long integrations into shorter ones, with max.
			duration of X seconds. It's the complement option to
			'merge', which does the opposite. Can also be used
			together with 'subscans.split' to break the shorter
			segments into separate scans altogether.
			@See: 'merge', 'subscans.split'
			
:: serial.[...]		@Advanced
			Specify settings to apply when the scan's serial number
			falls within the specified range inside the brackets.
			The range is simply an inclusive range of scan numbers
			separated by colon(s) ':' or hyphen(s) '-'. Wildcards 
			'*' can be used to specify open ranges. E.g.:

			   serial.[*--2593] rotation 15.3

			specifies an instrument rotation of 15.3 degrees up 
			until and including scan 2593.
			@See: 'mjd.[...]', 'date.[...]'

:: shift=X		@Expert
			@Since: 2.30
			Shift the data by X seconds relative to the frame 
			headers. It can be used to diagnose, or correct for,
			timing problems.

:: signal-response	@Expert
			This is diagnostic option. It affects the console
			output of decorrelation steps. When specified, 
			each decorrelation step will produce a sequence of 
			numbers, corresponding to the normalized covariances of 
			the detector signals in each correlated mode in the
			'modality'. The user may take this number as an 
			indication of the importance of each type of correlated 
			signal, and make decisions based on it, whether a 
			decorrelation step is truly necessary or not. Values
			close to 1.0 indicate signals that are (almost) 
			perfectly correlated, whereas values near zero are 
			indicative of negligible correations.
			@See: 'correlated.<?>', 'division.<?>', 'ordering' 

:: skydip		Reduce skydip data, instead of trying to make an 
			impossibly large map out of it :-). This option is
			equivalent to specifying 'source.type=skydip', which is
			activated conditionally, instead of an alias. The 
			reason for not using an alias in this case, is to 
			retain, independently, 'skydip' option branches.


:: skydip.attempts=N	@Advanced
			@Since: 2.34
			Try fit the skydip data multiple times, and pick the
			best of all for reporting. Useful for mitigating
			occasional convergence failures or getting stuck in
			local minima.

:: skydip.elRange=<min>:<max>	@Advanced
				@Since: 2.14
			Set the elevation range (in degress) to use for fitting
			the skydip model. In some cases either the data may be
			corrupted either at low elevations, or at high 
			elevations, or both, making it a useful option to 
			restrict the skydip data to the desired elevation 
			range. Use with caution to keep the skydip results
			robust!
			@See: 'skydip'

:: skydip.fit=<list>	@Expert
			Specify the list of parameters to fit for the skydip 
			model. The standard model is

			 y(EL) = kelvin * Tsky * (1-exp(-tau/sin(EL))) + offset

		        where:

			   kelvin	conversion from Kelvin to dataunits.
				   	(see: 'kelvin' and 'K2Jy')

			   Tsky	  	Sky temperature (in Kelvin).
				   	(see: 'skydip.Tsky')

			   tau	 	The in-band zenith opacity
				   	(see: 'skydip.tau')
						 
			   offset	An offset in dataunits 
			   		(see 'skydip.offset')

			The default is to fit 'kelvin', 'tau', and 'offset', 
			and assume that the sky temperature is close to 
			ambient. (The assumption on the sky temperature is not 
			critical as long as the conversion factor 'kelvin' is 
			fitted to absorb an overall scaling).
			@See: 'skydip.offset', 'skydip.tau', 'skydip.Tsky', 
			      'kelvin', 'K2Jy', 'dataunit'
					  
:: skydip.grid=X	@Advanced
			@Since: 2.33-2
			Set the elevation binning (arcsec) of the skydip data.
			@See: 'grid'

:: skydip.offset=X	@Expert
			Specify the (initial) offset value in dataunits
			@See: 'skydip.fit'

:: skydip.tau=X		@Advanced
			Specify the (initial) in-band zenith opacity.
			@See: 'skydip.fit'

:: skydip.Tsky=X	@Advanced
			Specify the (initial) sky temperature in Kelvins.
			By default the ambient temperature (if available) will 
			be used. This option can be use to override with a
			specific value.
			@See: 'skydip.fit'

:: show			@Since: 2.14-a2
			Try show the result of the reduction, if possible. 
			As of the introduction of this option, only skydip
			reductions use it (requires 'gnuplot' option to be set 
			also and gnuplot be installed.)
			Maps are expected to follow this directive soon also.
			Bath reductions should disable 'show'.
			@See: 'gnuplot'

:: skipFWFix            @Instrument: GISMO
			@Expert
                        @Since: 2.15-2
                        During 2013 Oct/Nov we had lost some data due to
                        firmware problems. Steve has attempted to reconstruct
                        as much of the affected frames as possible. At the same
                        the the reconstructed astrometry is flagged
                        accordingly. Therefore, it is possile for CRUSH to
                        ignore the reconstructed data if the user wishes to do

:: smooth=X		@Advanced
			Smooth the map by X arcsec FWHM beam. Smoothing
			helps improve visual appearance, but is also useful
			during reduction to create more redundancy in the data
			in the intermediate reduction steps. Also, smoothing
			by the beam is optimal for point source extaction from
			deep fields. Therefore, beam smoothing is default in
			with the 'deep' option (see 'deep.cfg').
			Typically you want to use some smoothing during 
			reduction, and you may want to turn it off in the 
			final map. Thus, you may have something like:

			  smooth=9.0			# 9" smoothing at first
			  iteration.[2]smooth=12.0 	# smooth more later
			  iteration.[last]forget=smooth # no smoothing at last

			Other than specifying explicit values, you can use
			the predefined values: 'minimal', 'halfbeam', '2/3beam'
			'beam', or 'optimal'.
			@See: 'smooth.optimal', 'final', 'source.filter', 'grid'
			
:: smooth.external	@Advanced
			Do not actually perform the smoothing set by
			the 'smooth' option. Instead, use the 'smooth'
			value as an assumption in calculating smoothing-related
			corrections. The option is designed for the reduction
			of very large datasets, which have to be 'split' into
			smaller, manageable sized chunks. The unsmoothed outputs
			can be coadded and then smoothed to the desired amount
			before feeding the result back for further rounds of
			reduction via 'source.model'
			@See: 'smooth', 'split', 'source.model'

:: smooth.optimal=X     @Expert
			Define the optimal smoothing for point-source
			extraction if it is different from beam-smoothing.
			For arrays, whose detectors are completely independent,
			beam-smoothing produces the optimal signal-to-noise
			for point sources. However, if the detectors are not
			independent, the optimal smoothing may vary. This is
			expected to be the case for some filled arrays, where
			one expects a certain level of beam-sized photon 
			correlations.
			@See: 'smooth'

:: source		Solve for the source model, or set options for it.

:: source.correct	@Advanced
			Correct peak fluxes for the point source filtering
			effect of the various reduction steps (default). The
			filtering of point sources is carefully calculated
			through the reduction steps, thus with the correction
			scheme, point source fluxes ought to stay constant 
			(within a few percent) independent of the pipeline
			configuration.
			@See: 'faint', 'deep', 'bright', 'ordering', 'whiten'

:: source.coupling	@Advanced
			(Re)calculate point source copling efficiencies
			(i.e., the ratio of point-source and sky-noise
			response) as part of the source modeling step. This is
			only really useful for bright sources.
			@See: 'source.coupling.range'

:: source.coupling.range=min:max	@Expert
					Specify the range of acceptable coupling
					efficiencies relative to the "average"
			of all pixels, when 'source.coupling' is used to 
			calculate these based on bright source responses. Pixels
			with efficiencies outside of the specified range will be
			flagged and ignored from further source modeling steps
			until these flags are cleared again in the reduction.
			@See: 'correlated.<?>.gainrange'

:: source.coupling.s2n=<min:max>	@Expert
					@Since: 2.34
			Set the acceptable range of S/N required in the map for
			using the position for estimating detector coupling
			gains when the 'source.copuling' option is enabled.
			@See: 'source.coupling'	

:: source.despike  	@Advanced
			Despike scan maps at. 
			Clearly you want to set X to be higher than the most 
			significant source in your map. Therefore it is only 
			really useful in 'deep' mode, where 5-sigma despiking
			is default (see 'deep.cfg').


:: source.despike.level=X	@Advanced
				Set the source despiking level to an S/N of 
				X. You probably want to set X to be no more 
		    	than about 10 times the most significant source in your
			map. Therefore it is only really useful in 'deep' mode, 
			where a  5-sigma despiking is default (see 'deep.cfg').
			@See: 'despike'	

:: source.filter   	Filter extended structures. By default the filter will
			skip over map pixels that are above the 'blanking' S/N 
			level (>6 by default). Thus any structure above this 
			significance level will remain unfiltered.
			Filtering is useful to get deeper in the map when 
			retaining the very faint extended structures is not 
			an issue. Thus filtering above 5 times the source size
			(see 'sourcesize') is default when the filter is used.
			See the advanced configuration section for further
			details on fine tuning the large-scale structure 
			filter.	

:: source.filter.blank=X	@Expert
				Set the blanking level of the large-scale
				structure (LSS) filter. Any map pixels with an
			S/N above the specified level will be skipped over, 
			and thus remain unaffected, by the filter.
			@See: 'source.filter.fwhm'

:: source.filter.fwhm=X	@Advanced
			Specify the Gaussian FWHM of the large-scale
			structure (LSS) filter. Values greater than
			about 5-times the beam size are recommended in order
			to avoid the unnecessary filtering of compact or point
			sources.
			@See: 'source.filter.blank'

:: source.filter.type=<type>	@Advanced
				Specify the type ('convolution' or 'fft') of 
				the large-scale structure filter. Convolution 
			is more accurate but may be slower than FFT, especially
 			for very large maps.

:: source.fixedgains	@Advanced
			Specifies to use the fixed source gains (e.g. from an 
			RCP file -- see 'rcp' key).
			Normally, crush calculates source gains based on the 
			correlated noise response and the specified point
			source couplings (e.g. as derived from the two gain
			columns of RCP files.). This option can be used to 
			treat the supplied source gains as static (i.e. 
			decoupled from the sky-noise gains).
			@See: 'source.coupling', 'pixelmap'

:: source.flatfield	@Advanced
			@Since: 2.34-2
			Use for deriving flatfields based on response to a 
			source. fro it to work effectively, you need a scan
			that moves brihgt source emission over all pixels. It
			is a soft option, defined in 'default.cfg', and it
			results in loading 'srcflat.cfg' for configuring
			optimal settings for source gain derivation.

:: source.inject=<path>		@Advanced
				@Since: 2.23
			Inject a source map into the timestreams. This may be
			useful for understanding the filtering properties. As
			such, the option would be used most commonly together
			with one of the 'jackknife' options, so any real
			emission cancels in the output map so that mainly only
			the injected source is seen.
			@See: 'source.inject.scale', 'jackknife', 
			      'jackknife.alternate', 'jackknife.frames',
			      'jackknife.channels'

:: source.inject.scale=X	@Advanced
				@Since: 2.23
			Scale the map by a factor X before injection into the
			timestream via the 'source.inject' option.
			@See: 'source.inject'

:: source.intermediates @Expert
			Write the maps made during the reduction into 
			'intermediate.fits' (inside the crush directory). 
			This option thus allows to keep an eye on 
			the evolution of maps iteration-to-iteration. Each 
			iteration will overwrite this temporary file, and it 
			will be erased at the end of the reduction.

:: source.margin=<pix>	@Advanced
			@Since: 2.16-1
			Add the specified number of pixels around the edges of
			the source map. It can be useful where the the map
			undergoes extrapolation which may place valid flux into
			these map pixels on the margins.

:: source.mem		@Advanced
			Use maximum-entropy method (MEM) correction to the
			source map. The maximum-entropy requirement supresses
			some of the noise on the small spatial scales, and
			pushes solutions closer to the zero level for low S/N
			structures. This increases contrast between significant
			source structures and background. It is similar to the
			MEM used in radio interferometry, although there are
			key differences. (For one, interferometry measures 
			components in the uv-plane, and MEM corrections are
			applied in xy coordinate space. For crush, both the
			solutions and the corrections are applied in the same
			configuration space.)
			@See: 'source.mem.lambda'

:: source.mem.lambda=X	@Advanced
			Specify the desirability of MEM solutions 
			relative to the maximum-likelihood solution.
			Typical values of lambda are in the range 0.1--1, but
			higher or lower values may be set to give extra weight
			towards one type of solution.

:: source.model=<file>  @Advanced
			Specify a in initial source model to use in the
			reduction. This may be useful when reducing 
			large datasets where all data cannot be reduced 
			together. Instead the data can be split in manageable 
			sized chunks, which are reduced separately. The results 
			can be coadded with the 'coadd' utility to create a 
			composite map. This may be further manipulated (e.g. 
			s/n clipping, smoothing, filtering etc.) with 
			'imagetool' before feeding back into another round of 
			reduction. See more in the README on how to deal with
			very large data sets.
			Clipping and blanking settings are usually altered
			(see 'default.cfg') when an a-priori source-model is
			thus defined.
			@WARNING: This feature is not yet thorougly tested.
		 		  Use at you own risk... 
			@See: 'smooth.external', 'clip', 'blank'

:: source.nosync	@Expert
			Do not bother synching the source solution back into the
			raw time-stream. This saves a bit of time in the last
			round of most reductions, when the 'source' is the
			last step in the pipeline, and the residuals are not
			used otherwise, e.g. by 'write.covar', 'write.ascii' or
			'write.spectrum'
			@See: 'write.covar', 'write.ascii', 'write.spectrum'

:: source.polar  	@Instrument: PolKa
			@Advanced
			Specify to yield polarization data (I,Q and U)
			rather than simply producing a total-power image. The
			option obviously only affects instruments that measure
			polarization, anbd will be ignored otherwise.
			You can also use the shorthand 'pol' to the same 
			effect.
			@See: 'pol', 'spf', 'waveplate.refangle', 'analyzer'

:: source.polar.angles		@Instrument: PolKa
				@Since: 2.11
				@Advanced
			Write an image of the polarization angles also. The
			shorthand 'spa' can also be used.
			@See: 'spa'

:: source.polar.fraction	@Since: 2.10
				@Instrument: PolKa
				@Advanced
			Write an image of the polarized power fraction as well
			as the default polarization products (N, Q, U and the
			derivatives I & P). You can also use the shorthand 
			'spf' to the same effect, and can control the clipping 
			of the noisy bits via the 'rmsclip' sub-option.
			@See: 'spf', 'source.polar', 
			      'source.polar.fration.rmsclip'

:: source.polar.fraction.rmsclip=X	@Since: 2.10
					@Instrument: PolKa
					@Expert
			Set the maximum rms for the unflagged points in the
			polarization fraction image. The default value is 0.03
			(i.e. 3% rms). You can also use the shorthand version
			'spf.rmsclip'.
			@See: 'spf', 'source.polar.fraction' 

:: source.redundancy=N	@Expert
			Specify the minimum redundancy (N samples) that
			each scan-map pixel ought to have in order to be
			considered valid. Pixels with redundancies smaller than
			this critical value will be flagged an not used in
			the composite source mapmaking.

:: source.sign=<spec>	@Since:2.15-2
			Most astronomical sources have a definite signedness.
			For continuum, we expect to see emission, except when
			looking at SZ clusters at 2-mm, which have a unique
			negative signature. CRUSH can do a better job if the
			signature of the source is predetermined. The sign
			specification can be '+', '-' or '*', or 'positive'
			'negative', 'pos', 'neg', 'plus', 'minus' or 'any' as
			well as a number (positive, negative or zero).
			When not set, the default is to assume that sources may
			be of either sign (same as '*', '0', or 'any').
			The signature determines how source clipping and
			blanking are implemented.
			@See: 'clip', 'blank'

:: source.type=<type>	By default, crush will try to make a map from
			the data. However, some istruments may take
			data that is analyzed differently. For example, you 
			may want to use crush to reduce pixel maps (to
			determine the positions of your pixels on sky), or
			skydips (to derive appropriate opacities), or do
			point source photometry. Presently, the following
			source types are supported accross the board:
		
			   map 		Make a map of the source (default)

			   skydip	Reduced skydips, and determine 
					opacities by fitting a model to it.

			   pixelmap	Create individual maps for every
					pixel, and use it to determine their
					location in the field of view.

			   null		Do not generate a source model.
					Useful for lab/diagnostic reductions.
	
			Note, that you may also just use 'skydip' and 
			'pixelmap' shorthands to the same effect. E.g.

			  > crush [...] -skydip [...]

			@See: 'skydip', 'pixelmap'


:: sources=<filename>	@Advanced
			@Since: 2.02
			Insert test sources into the data, from a catalog 
			specified by <filename>. You can find an example
			catalog in the crush directory, as 'example.mask'.
			The sources are inserted at the beginning of the
			reduction, with the default pixel gains. Since the
			gains are normally adjusted during the reduction the
			recovered source is expected to yield slightly 
			different flux, typically by a few percent. You can
			get a more accurate test calibration by using
			fixed source gains (i.e. decoupling these from the
			sky noise gains) via the 'source.fixedgains' option.
			Thus, the default configuration sets 
			'source.fixedgains' together with the 'sources' option.
			@See: 'source.fixedgains' 

:: sourcesize=X		This option can be used instead of 'extended' in 
			conjunction with 'faint' or 'deep' to specify the 
			typical size of sources (FWHM in arcsec) that are 
			expected. The reduction then allows filtering 
			structures that are much larger than the specified 
			source-size...
			If 'sourcesize' or 'extended' is not specified, then 
			point-like compact sources are assumed.	
			The sourcesize helps tune the 1/f filter (see 'drifts')
			optimally. The 1/f timescale is set to be the larger
			of the 'stability' timescale or 5 times the typical 
			source crossing time (calculated via 'sourcesize').
			Note, that noise whitening will mute the effect of
			this setting almost completely...
			@See: 'faint', 'extended', 'whiten'

:: spa			@Alias --> 'source.polar.angles'
			@Since: 2.11

:: spectral.grid=X      @Instrument: HIRMES
			@Advanced
			@Since: 2.42
                        Specify the bin spacing in the spectral dimension to
                        X, in the units set by 'spectral.unit'. When present
                        this option supercedes the 'spectral.R', which
                        is an elternative way to set the spectral bin size.
                        @See: 'spectral.unit'

:: spectral.obs         @Instrument: HIRMES
                        @Since: 2.42
                        Output spectra in the observing frame rather than the
                        default rest frame.

:: spectral.R=X		@Instrument: HIRMES
			@Advanced
			@Since: 2.42        
			Specify a spectral resolving power X (f/df) at the
                        reference frequency of observation. This option is used
                        only if the spectral bin (grid) size is not explicitly
                        defined via `spectral.grid`.
                        @See: `spectral.grid`

:: spectral.unit=<spec>	        @Instrument: HIRMES
                                @Since: 2.42       
                        Specify the unit of the spectral axis in the output 
                        data. It can be a wavelength unit, such as 'um' 
                        (micron) or a frequency unit, such as 'GHz'.
                        @See: 'unit'

:: spf			@Alias --> 'source.polar.fraction'
			@Since: 2.10

:: split		A convenience key for adjusting options for very large
			data sets, which have to be split into manageable sized
			chunks in the reduction. See the README for more
			information on the reduction of very large data sets.
			@See: 'smooth.external', 'source.model'

:: squids		@Alias -> correlated.squids
			@Instrument: ASZCA, SABOCA
			@Advanced
			Enable SQUID decorrelation or set options for it.
			@See: 'correlated.<?>'

:: stability=X		@Expert
			Specify the instrument's 1/f stability time scale in 
			seconds. This value is used for optimizing reduction 
			parameters when (e.g. the filtering time scale for the 
			'drifts' option) when these are not explicitly 
			specified.
			@See: 'drifts', 'sourcesize'

:: subarray=<list>	@Expert
			@Instrument: SCUBA-2, HAWC+
			@Since: 2.30
			Restrict the analysis to just the selected subarrays.
			For SCUBA-2, the list is a comma-separated list of
			letter codes 'at' thru 'd', E.g.:

			  > crush scuba2 -subarray='a,b' [...] 

			For HAWC+ the list consists of the subarray ids: 'R1', 
			'R2' and 'T1', 'T2', and may also use 'R' (same as 
			'R1,R2') or 'T' (same as 'T1,T2'). E.g. 

			  > crush hawc+ -subarray='R1,T1' [...]
				 

:: <subarray>.pixelsize=X,Y	@Expert
				@Instrument: SCUBA-2
				@Since: 2.01-1
			Specify the pixel spacing (in arcseconds) of the 
			<subarray> pixels. Pixels positions are then calculated 
			assuming a rectangular grid with the given spacing.
			E.g.: s8d.pixelsize=6.2,6.1
			@See: '<subarray>.position', '<subarray>.rotation'

:: <subarray>.position=X,Y	@Expert
				@Instrument: SCUBA-2
				@Since: 2.01-1
			Defines the position of the the <subarray> center 
			relative to the pointing center of the instrument as
			comma separated coordinates (in arcseconds) in the
			Nasmyth focal plane.
			E.g.: s4a.position=-12.2,5.3
			@See: '<subarray>.pixelsize', '<subarray>.rotation'

:: <subarray>.rotation=X	@Expert
				@Instrument: SCUBA-2
				@Since: 2.01-1
			Specify the rotation angle (in degrees) of the 
			<subarray>. E.g.: s4a.rotation=45.0 
			@See: '<subarray>.pixelsize', 'subarray.position',
			      'rotation'.

:: subscans.merge	@Expert
			@Since: 2.01-1
			Specifies that the integrations (subscans) in a scans
			should be merged into a single timestream, with
			null frames filling potential gaps at the boundaries
			to ensure proper time-spacing of all data (for time
			window processing or FFT).
			@Since: 2.30
			Now available for all instruments (previously it was
			for the then proprietary SCUBA-2 module only).
			@See: 'subscans.split'

:: subscans.merge.maxgap=X	@Expert
				@Since: 2.30
			Merging subscans will pad gaps between them with null
			frames as needed. Use this option to limit how much 
			padding is allowed. If the gap between two consecutive
			subscans is larger than the maximum gap (seconds)
			specified by this option, then the the merge will
			continue in a separate subscan.

:: subscans.minlength=X	@Expert
			@Since: 2.05
			Set the minimum length of integrations (subscans) to
			X seconds. Integrations (subscans) shorter than the
			specified value will be skipped during the scan
			reading phase.
			Most CRUSH reductions rely on the background variations
			to create signals from which detector gains can be
			estimated with the required accuracy. Very short
			integrations may not have sufficient background signals
			for the robust estimation of gains, and it is thus
			best to simply ignore such data.

:: subscans.split	@Expert
			@Since: 2.01-1
			Instruct CRUSH to split subscans into separate
			scans. This is practical to speed up the reduction
			of single scans with many subscans on machines with
			multi-core CPUs, since CRUSH does not process
			integrations in parallel, but it does parallel process
			scans.
			@See: 'subscans.merge'

:: supergalactic	@Alias -> system=supergalactic
			Make maps in supergalactic coordinates.
			@See: 'system'

:: system=<type>	Select the coordinate system for mapping. The default
			is 'equatorial'. Other possibilities are 'horizontal'
			'ecliptic', 'galactic' or 'supergalactic', 'focalplane'
			or 'native'. Most of these values is additionally 
			aliased to simple keys. Thus, you may use:
			
			   > crush -galactic [...]
			   
			as a shorthand for '-system=galactic'.
			@See: 'altaz', 'equatorial', 'ecliptic', 'galactic',
			      'supergalactic', 'radec', 'horizontal', 
			      'focalplane'	       

:: SZ                   @Instrument: GISMO
			@Since: 2.15-2
                        Optimize reduction for the detection of Sunyaev-
                        Zel'dovich signals (decrements). The SZ option is
                        really just a trigger condition for activating other
                        settings. Check the configuration files under
                        the gismo/ crush folder (esp. 'default.cfg) to see
                        what this does exactly.

:: tau=<arg>		Specify an in-band zenith opacity value to use. E.g.:

			  > crush [...] -tau=0.344 [...]			

			For some instruments, the argument can also specify a 
			file-name with lookup information (usually containing 
			tau values from the radiometer or from the skydips),
			or tau in another band (See 'tau.<?>' option) with an
			appropriate scaling relation to in-band values (see
			'tau.<?>.a' and 'tau.<?>.b' options).
			
			When lookup tables are used, the tau values will be 
			interpolated for each scan, as long as the scan falls 
			inside the interpolator's range. Otherwise, tau of 0.0 
			will be used. The filename may contain references to 
			environmnent variables enclosed in {} brackets. E.g.:

			  tau={$HOME}/laboca/tau.dat
			  
			Some instrument (e.g. SHARC-2) may use measurements 
			from a 225GHz radiometer, or some other source, from
			which values can be scaled to in-band. E.g. the 
			combination of options:

			  tau.225GHz=0.033
			  tau=225GHz

			can be used to set tau to it's 225GHz equivalent value.
			(e.g. for SHARC-2).

			SHARC-2 also allows for setting tau to 'direct', for
			a calibrated conversion of bolometer DC levels to
			in-band line-of-sight opacities, when in '350um' mode.
	
			The argument may also be 'tables' for SHARC-2 and MAKO
			to specify CSO tau tables. See 'tau.tables' for 
			details.

			@see: 'tau.<?>', 'tau.<?>.a', 'tau.<?>.b', 'tau.tables'


:: tau.<?>=X		@Advanced
			Specify the tau value X for <?>. The <?> can stand for
			any user-specified relation. Some useful conversion
			relations are predefined for certain instruments. E.g.
			some typical values may be one of the following:

			   225GHz	The 225GHz radiometer value.

			   350um	The tau value for the 350um tipper.

			   pwv		millimeters of precipitable water vapor.

			The values will be scaled to in-band zenith opacities 
			using the linear scaling relations defined via the 
			'tau.<?>.a', and 'tau.<?>.b' constants.
			@See: 'tau', 'tau.<?>.a', 'tau.<?>.b'

:: tau.<?>.a=X		@Expert
			Define the scaling term for the opacity measure <?>.
			Zenith opacities are expressed in a linear relationship
			to some user-defined tau parameter t as:

			  tau(<?>) = a*t + b

			This key sets the linear scaling constant 'a' in the
			above equation, while 'tau.<?>.b' specifies the offset
			value. By default the parameter t is set to be the
			225GHz radiometer value (This is achived by setting
			"tau.225GHz.a=1.0" and "tau.225GHz.b=0.0" in 
			"default.cfg").
			@See: 'tau.<?>'

:: tau.<?>.b=X		@Expert
			Set the offset value in a linear tau scaling 
			relationship.
			@See: 'tau.<?>.a' for details.


:: tau.jctables=<spec>	@Advanced
			@Since: 2.20
			@Instrument: SHARC, SHARC-2, MAKO, MAKO-2, SCUBA-2
			Specify the location (folder) of the JCMT 183 GHz tau
			tables. The argument can point to a local directory
			or an online resource on the web (URL). E.g.:

			  http://www.jach.hawaii.edu/weather/opacity/mk/archive			
			If the JCMT lookup fails (e.g. because no data is
			available for the specific date, or using CRUSH 
			offline), then a fallback option may be specified via
			the 'maitau.fallback' key. 
			@See: 'tau.tables', 'maitau.fallback'

:: tau.tables=<path>	@Since: 2.14
			@Instrument: SHARC, SHARC2, MAKO, MAKO-2
			Path to the directory containing the CSO tau tables.
			The files are assumed to be named by date as 
			<yyMMdd>.dat, e.g.: '130421.dat'.
			The tables are usually found at:
			   
			  kilauea:/bigdisk/opt/uip/data/opacity/		

			@See: 'tau', 'tau.window'


:: tau.timezone=AAA	@Advanced
			@Instrument: GISMO			
			@Since: 2.15-2
			Specify the timezone, such as 'UTC' or 'CET' in which
			the tau lookup table is specified.
			@See: 'tau.window'

:: tau.window=X		@Expert
			@Telescope: APEX, CSO, JCMT
			@Since: 2.13
			Set the 1-sigma Gaussian weighting window (in hours) 
			for deriving local weighted average tau values from a 
			table of skydip/tau measurements.
			@GISMO: since 2.15-2.
			@See: 'tau', 'scale.window'

:: threads=N		@Since: 2.30
			@Expert
			Specify the actual number of threads that CRUSH should
			use. By default CRUSH will run as many threads as there
			are (virtual) cores in the host machine. Before, you
			could only alter that behaviour by instructing crush to
			use some number fewer than optimal ('idle' option).
			This new option gives the user explicit control on the
			threading, although it only really serves the purpose
			of testing and checking for scalability. In most other
			scenarios, users should stay away from tryinf to manage
			threading, and let crush decide what's optimal.
			@See: 'idle'

:: time-weighting	@Alias: -> weighting.frames
			@Advanced
			Turn on time weighting or set options for it.
			@See: 'weighting.frames'


:: twisting		@Alias: -> correlated.twisting	
			@Instrument: LABOCA
			@Expert
			Enable the decorrelation of signals that correspond to
			twisting flexible band cables, or set options for it.
			@See: 'correlated.<?>', 'cables'

:: uniform		@Expert
			Instruct the use uniform pixel gains initially instead 
			of the values read from the appropriate pixel data file
			@See: 'pixeldata'

:: unit=<name>		Set the output units to <name>. You can use either the
			instrumental units (e.g. 'V/beam' or 'counts/beam') or
			the more typical 'Jy/beam' (default), as well as their
			common multiples (e.g. 'uJy/beam', or 'nV/beam').	
			@See: 'dataunit', 'jansky'

:: .unlock		@Since: 2.31
			Release the lock on the parent option, thus allowing
			it to be changed again (e.g. by a conditional). E.g.
			Suppose you locked the 'stability' option via:

			  > [...] -stability.lock=5.0

                        on the command line. You can release that lock later
			via:

			  > [...] -stability.unlock

			@See: '.lock', '.unlock', '.relock'


:: vclip=<arg>		@Advanced
			Clip data where the field scan velocity is outside
			the specified range (min:max in arcsec/sec). The 
			successfull disentangling of the source structures from 
			the various noise terms relies on these being separated
			in frequency space. With the typical 1/f type limiting 
			noise, this is harder when the scan speed is low s.t. 
			the source signals occupy the low frequencies. 
			Therefore, requiring a minimum scanning speed is a 
			good idea...
			On the other side, too high scanning speeds will smear
			out sources, if the movement between samples is larger
			than ~1/3 beam.
			The value 'auto' can be specified to set the velocity
			clipping range optimally based on the typical scanning
			speeds.
			@See: 'vclip.strict', 'aclip', 'resolution'

:: vclip.strict		@Expert
			@Since: 2.34
			When present, CRUSH will discard any frames outside of
			the acceptable range of mapping speeds (as defined by
			the 'vclip' option), rather than the default approach
			of simply flagging slow motion for source modelling
			only. 


:: ver.[<range>] key=value	@Since: 2.11
				@Instrument: GISMO
				@Expert
			Set options depending on the FITS merge version. E.g.
			
			   ver.[<1.7] pointing.model=old.model
			   ver.[1.6--1.7] forget=pointing.model.static

			@See: 'ver'

:: ver=X		@Since: 2.11
			@Instrument: GISMO
			@Expert
			Manually override the FITS merge version, and ignore
			the information stored in the FITS itself.

:: veryquiet		@Since: 2.33
			@Advanced
			Suppress most console output, except warnings and 
			errors. (Unlike 'quiet', not results or notifications 
			will be reported).
			@See: 'quiet'

:: waveplate.channel=N  @Instrument: PolKa
			@Expert
			Specify the LABOCA channel (counting from 1) that
			carries the waveplate phase information. The waveplate
			phases are critical to recovering the polarization
			information from the data.
			@See: 'waveplate.fchannel', 'waveplate.refangle'

:: waveplate.counter	@Instrument: PolKa
			@Advanced
			@Since: 2.11
			Occasionally the waveplate spins backwards. This option
			lets you reduce such data, provided you know when this
			happened.

:: waveplate.fchannel=N	@Instrument: PolKa
			@Expert
			The LABOCA channel number (counting from 1),
			which contains the frequency information for the last
			waveplate cycle. This information is not used by crush
			really, but may point the user to where to find this
			information in the raw data, if one wishes to look into
			the details.
			@See: 'waveplate.channel'

:: waveplate.fix	@Instrument: PolKa
			@Advanced
			@Since: 2.40
			Recalculate the waveplate data from the reconstructed
			waveplate crossings. Requires timestamp information via
			'waveplate.tchannel'.
			@See: 'waveplate.despike', 'waveplate.tchannel' 

:: waveplate.frequency=X	@Instrument: PolKa
				@Obsolete
				@Expert
				Specify the waveplate frequency (in Hz) to 
			assume when detailed waveplate information is not 
			readily available. The waveplate angle of the first
			frame can be set via 'waveplate.refangle'.
			@See: 'waveplate.channel', 'waveplate.refangle'

:: waveplate.incidence=X	@Instrument: PolKa
				@Expert
				@Since: 2.11
			The waveplate incidence angle from normal, in degrees.
			@See: 'waveplate.incidence.phase'

:: waveplate.incidence.phase=X	@Instrument: PolKa
                        	@Expert
                        	@Since: 2.11
			The waveplate phase (in degrees) of the plane of
			incidence, measured from the reference position in the
			direction of waveplate rotation.
			@See: 'waveplate.incidence'
 
:: waveplate.jitter=X	@Instrument: PolKa
			@Expert
			Specify the typical fractional waveplate jitter.
			This information is used for designing optimal notch
			filters for the total-power mode to reject any 
			waveplate modulated residues. This option has been
			obsoleted by the new time-domain filter, and will 
			dissappear in future releases.
			@See: 'waveplate.channel'

:: waveplate.oversample=X	@Instrument: PolKa
				@Expert
				@Since: 2.04
			Define the oversampling rate for the total-power 
			modulation removal. Typically, a waveplate rotation 
			(1.560 Hz) is 16 samples (at 25Hz sampling rate),
			only coarsly resolving the power modulation waveform.
			Because the waveplate rotation is not completely 
			synchronous with the acquition, it may help to model
			the waveform at somewhat higher resolution for a better
			removal of the unwanted total-power modulation 
			signals. The default value is 1.0.
			@See: 'waveplate.channel'

:: waveplate.refangle=X	@Instrument: PolKa
			@Advanced
			Set the waveplate angle at its reference 
			position. The calibration of this position is necessary
			for obtaining meaningful polatization angles. Without
			it only the polarized fluxes, or polarization fractions
			can be measured. The calibration of the reference angle
			requires measurements on sources of known polarization
			(e.g. a wire grid in the pupil)
			@See: 'waveplate.channel'

:: waveplate.tchannel=N	@Instrument: PolKa
			@Expert
			@Since: 2.11
			The channel that holds the timing offsets to the last
			waveplate timestamp. This information can be used by
			CRUSH to fully reconstruct the waveplate motion (at
			least to the timestamping accuracy).

:: waveplate.tp		@Instrument: PolKa
			@Expert
			@Since: 2.40
			Use the total power modulation signature to determine
			waveplate phases. Use with caution and onl if the
			waveplate information is not otherwise present, such
			as during 6-8 December 2011.
			@See: 'waveplate.tpchannel', 'waveplate.tpharmonic'

:: waveplate.tpchannel=N	@Instrument: PolKa
				@Expert
				@Since: 2.11
			Reconstruct the waveplate data, when this is not
			recorded (such as for two days in Dec 2011), from the
			total power-modulation of the specified channel.
			The harmonic and relative phase of the total power
			modulation (for H and V analyzers respectively) are set
			by 'waveplate.tpharmonic', 'analyzer.h.phase' and 
			'analyzer.v.phase'
			@See: 'waceplate.tpharmonic', 'analyzer.h.phase'
			      'analyzer.v.phase'

:: waveplate.tpharmonic=N	@Instrument: PolKa
				@Expert
				@Since: 2.11
			The harmonic of the waveplate frequency that should be
			used for the waveplate phase reconstruction, when the
			waveplate phase data is not recorded.
			@See: 'waveplate.tpchannel'

:: weighting		Derive pixel weights based on the rms of the unmodelled
			timestream signals.

:: weighting.frames	@Advanced
			In addition to pixel weighting, time-weights
			can also be calculated to allow for non-stationary 
			noise. 
			@See: 'weighting.frames.resolution', 'time-weighting'

:: weighting.frames.noiserange=min:max	@Expert
					Set the range of acceptable temporal 
					noise variation.
			Hyphen(s) '-' can also be used instead of colon(s) ':'
			to separate the min and max values. Wildcards can '*'
			indicate open ranges. E.g.
			
			   weighting.frames.noiserange=0.1:*

			@See: 'weighting.noiserange'

:: weighting.frames.resolution=X	@Expert
					By default all exposures are weighted 
					indepently. With this
			option set, weights are derived for blocks of exposures
			spanning X seconds. The value 'auto' can be also used
			to match the time-constant to that of 'drifts'. 
			Time weighting is often desired but can cause 
			instabilities in the reduction, especially if the 
			time-scale is mismatched to the other reduction steps.
			Adjust the timescale only if you really understand what
			you are doing.	
			@See: 'drifts'

:: weighting.method=<name>	@Advanced
				Set the method used for deriving pixel weights 
			from the residuals. The following methods are 
			available:

			   rms	          Standard rms calculation.
			   robust         Use robust estimates for the standard 
			   		  deviation.
			   differential   Estimate noise based on pairs of data
			   		  separated by some interval in time.
					  

:: weighting.noiserange=min:max	@Advanced
				Specify what range of pixel noises are
				admissible, relative to the median pixel
			noise. Pixels that fall outside of the specified range 
			(min and max) will be flagged. Hyphen(s) '-' can also be
			used instead of colons(s) ':' to specify the ranges. 
			Wildcards '*' can specify open ranges. E.g.
			
			   weighting.noiserange=0.3:*

			@See: 'weighting.frames.noiserange'

:: weighting.phases	@Expert
			@Since: 2.43
			@Was: 'phaseweights' (2.15 - 2.42)
			When set, CRUSH will calculate proper noise weights
			for the phase data as well as the high-frequency 
			time-stream, under the expectation that the phase
			noise can be dominated by 1/f-type behaviour on the
			relevant timescales. The calculation of phase weights
			improves the reliability of the photometry.
			@See: 'weighting', 'phases', 'chopped'
	
:: weighting.scans	@Advanced
			If specified, each scan gets an assigned weight
			with which it contributes to the composite map.
			This weight is measured directly from the noise 
			properties of the produced map. 

:: weighting.scans.method=<name>	@Advanced
					'robust' or 'maximum-likelihood'.


:: whitelist=<list>	Remove <option> from the blacklist, allowing
			it to be set again if desired. Whitelisting
			an option will not reinstate it to its prior value. 
			After whitelisting, you must explicitly set it again, 
			or 'recall' or 'replace' it to its prior state.

:: whiten		@Alias -> 'filter.whiten'
			@Advanced

:: whiten.level=X	@Alias -> 'filter.whiten.level'
			@Advanced

:: whiten.minchannels=N	@Alias -> 'filter.whiten.minchannels'
			@Expert
			@Since: 2.01-1
	
:: whiten.proberange=<spec>	@Alias -> 'filter.whiten.proberange'
				@Expert
				@Since 2.00-b2

:: wiring=<filename>	@Expert
			This option is commonly used to specify a
			file containing the wiring information of
			the detectors, which can be used to establish the
			typical pixel groupings of instruments. There is no
			standard format for the wiring file (it may be
			different for each instrument), and not all instrument
			may use such information.
			@See: 'pixeldata', 'rcp'


:: write.ascii		@Advanced
			Write the residual timestreams into an ASCII table.
			The file will contain as many columns as there are
			pixels in the reduction (see 'noslim'), each 
			corresponding to a pixel time-stream. The first row 
			contains the sampling rate (in Hz). Flagged data is 
			indicated with a NaN character.
			@See: 'noslim', 'write.spectrum'			

:: write.coupling=<list>	@Since: 2.16
				@Advanced
			Measure and write coupling gains to the given signals.
			(Coupling gains are similar to correlation coefficients
			but normalized differently so that they can be used
			directly to remove the correlated signal from the
			timestreams).
			E.g.

			  write.coupling=telescope-x,accel-mag

			will write out the coupling gains of each detector to
			the telescope azimuth motion ('telescope-x') and
			scalar acceleration ('accel-mag').
			@See: 'list.modalities', 'correlated.<?>',
				'write.coupling.spec'


:: write.coupling.spec=<list>	@Since: 2.16
				@Advanced
			Measure and write coupling specta (similar to 
			correlation spectra, but with a gain-type normalization
			so that the values can be interpreted directly as gains
			by which the correlated signal can be removed from the
			timestream data). The argument is a list of modality
			names, such as 'telescope-x' or 'accel-mag'
			@See: 'write.coupling.spec.windowsize', 
			 	'list.modalities', 'correlated.<?>',
                                'write.coupling.spec'

:: write.coupling.spec.windowsize=N	@Since: 2.16
					@Expert
			Specify the window size (as N downsampled samples) on
			which to measure the coupling spectra. The default
			is to measure on the longest meaningful timescale
			as defined by 'drifts'.
			@See: 'write.coupling.spec', 'drifts'

:: write.covar[=<list>]	@Expert
			Write covariance data. If no argument is
			specified, CRUSH will write the full 
			pixel-to-pixel covariance data as a FITS image. The 
			optional argument can specify the ordering of the 
			covariance matrix according to pixel divisions. Each
			group in the pixel division will be blocked together
			for easy identifycation of block-diagonal covariance
			structures. Other than the division names, the list
			can contain 'full' and 'reduced' to indicate the full
			covariance matrix if all instrument pixels, or only
			those that were used in the reduction (see 'noslim').
			@See: 'division.<?>', 'noslim'

:: write.covar.condensed	@Since: 2.32
				@Expert
			When writing covariance matrices, write only 'live'
			channels, i.e. those that are unflagged by the 
			reduction. This results in a covariance matrix without
			gaps. The downside is that identifying particular
			pixels/channels may be difficult in that form.
			@See: 'write.covar'

:: write.eps		@Since: 2.14
			Write final result into an EPS image, if available.
			As of 2.15, both photometry and 'skydip' reductions 
			support EPS output but only when the 'gnuplot' options 
			is also set.
			@See: 'gnuplot', 'write.png', 'skydip'


:: write.fieldspec      @Instrument: HIRMES
                        @Since: 2.42
                        Write the aggregate 1D field spectrum as and ASCII
                        table also. This data can also be readiliy plotted
                        using gnuplot if the '.eps' and/or '.png' sub-options
                        are set (see below). The plot can be customized via
                        a set of sub-options '.lt', '.lw', '.pt', '.ps' and
                        '.style' in accordance with gnuplot's capabilities.
                        @See: 'gnuplot'

:: write.fieldspec.eps  @Instrument: HIRMES
                        @Since: 2.42
                        Create an EPS plot from the aggregate 1D field spectrum
                        using gnuplot.
                        @See: 'gnuplot'

:: write.fieldspec.lt=N         @Instrument: HIRMES
                                @Since: 2.42        
                        Set the plot line type to gnuplot's built-in type N 
                        (integer).

:: write.fieldspec.lw=X         @Instrument: HIRMES
				@Since: 2.42
                        Set the plot line with to X points wide, e.g. 2.5.

:: write.fieldspec.png  @Instrument: HIRMES
                        @Since: 2.42
                        Create a PNG plot from the aggregate 1D field spectrum 
                        using gnuplot. A set of sub-options can be used to 
                        customize the appearance.

:: write.fieldspec.png.bg=<color>       @Instrument: HIRMES     
                      	                @Since: 2.42
                        Set the PNG background color to the specified color 
                        (e.g. 'white' or '#FFFFFF', or 'transparent').

:: write.fieldspec.png.size=NxM         @Instrument: HIRMES
                                        @Since: 2.42
                        Set the PNG output size to N by M pixels

:: write.fieldspec.ps=X         @Instrument: HIRMES
                                @Since: 2.42
                        Set the plot point size scale factor to X, e.g. 1.5.

:: write.fieldspec.pt=N         @Instrument: HIRMES
                                @Since: 2.42        
                        Set the plot point tyle to gnuplot's built-in type N 
                        (integer).

:: write.fieldspec.show         @Instrument: HIRMES        
                                @Since: 2.42
                        Display the plot on screen right away.

:: write.fieldspec.style=<plotstyle>     @Instrument: HIRMES 
                                         @Since: 2.42
                        Set the gnuplot plotting style for 1D data. E.g. 
                        'histep', or 'points' or 'lines' or 'linespoints'

:: write.flatfield[=<path>]	@Expert
				@Since: 2.31
                        	Write a DRP flatfield FITS file, to be used by
			the chop-nod pipeline. The optional argument can 
			specify the FITS file's name. Otherwise, a default
			name is used, containing the scan's ID, and placed in
			the the directory specified by 'outpath'.
			The file format is specified by Marc Berthoud.
			@See: 'outpath'

:: write.flattened      @Instrument: HIRMES
                        @Since: 2.42
                        Write a flattened 2D (monochrome) FITS image also.

:: write.flattened.gzip @Instrument: HIRMES
			@Since: 2.42
			Compress flattened image with gzip.
			@See: 'gzip'

:: write.pixeldata	@Expert
			Write the pixel data file (gains, weights, 
			flags). The oputput will be 'pixel-<scanno>.dat'.
			You can use these files to update instrumental
			defaults in the instrument subdirectory. E.g., you can 
			overwrite 

				laboca/laboca-pixel.dat

			to change what default pixel settings to use.
			@See: 'rcp', 'wiring'

:: write.png		@Since: 2.04
			Write a PNG thumbnail for the final result. The PNG
			image has the same name as the output file but with
			'.png' appended.
			@See: 'write.png.size', 'write.png.color', 
			      'write.png.bg', 'write.png.plane'

:: write.png.bg=<value>		@Since: 2.04
				Set the background color of the PNG image. You
			can use hexadecimal values, e.g. '0xFFFFFF' (in RGB) 
			for white. The value 'transparent' can be used also.
			@See: 'write.png.color'

:: write.png.color=<name>	@Since: 2.04
				Set the color scheme used for rendering the 
			PNG image. The following schemes are supported:

			   'colorful'
			   'rainbow'
			   'temperature'
			   'doppler'
			   'grayscale'
			   'daytime'
			   'nighttime'
			   'blue'
			   'glacier'
			   'orange'
			   'bb'

			The default is 'colorful'.
			@See: 'write.png'

:: write.png.crop=<corners>	@Since: 2.16
				Set rectangular bounds to the PNG output image
			in the instrument's native size unit (usually arcsecs).
			The argument is usually a comma separated list of
			corners, relative to the source position:

				dXmin,dYmin,dXmax,dYmax
				
			If a single value is given then the PNG output will 
			be a square area with +/- that size in X and Y. If
			2 or 3 values are supplied, the missing offsets will
			be assumed to be the the negative equivalent to the
			coordinates given. Thus:

				90 = 90,90,-90,-90
				90,60 = 90,60,-90,-60
				90,60,-45 = 90,60,-45,-60

			@See: 'write.png'		

:: write.png.plane=<name>	@Since: 2.11-2
				Selects the FITS image plane to write into the 
				PNG. The argument can be one of: 'flux', 
			'noise', 'weight', 'time', or 's2n'. For other values, 
			CRUSH defaults to writing the 'flux' image.
			@See: 'write.png'

:: write.png.size=<size>	@Since: 2.04
				Set the size of the PNG thumbnails. You can
			specify both a single integer for square images or
			two integers separated by 'x' or ',' e.g. '640x480'.
			The default size is 300x300.
			@See: 'write.png'

:: write.png.smooth=<spec>	@Since: 2.16
				Specify how much to smooth the PNG output. The
			option works the same as the regular 'smooth' option
			for FITS images, but is not completely independent from
			it. PNG images are always smoothed as much as required
			by 'smooth', and this option is only effective if the
			PNG smoothing is larger.
			@See: 'smooth'

:: write.png.scaling=<type>	@Since: 2.16
				Specify what scaling method to use for 
			generating the PNG image output. The <type> argument
			can be one of the following scaling relations:

				linear	Linear scaling
				log	Logarithmic 
				sqrt	Square-root scaling

			The default value is 'linear'.
			@See: 'write.png'
	
:: write.signals	@Expert
			Write out all the correlated signals that were
			calculated in the reduction as ASCII timestreams.
			Each signal mode is written in its own file, named
			after the mode's name, and carrying a '.tms' extension.
			The files are simple ASCII timestreams with the 
			sampling frequency appearing in the first row.

:: write.scandata	@Advanced
			Whether or not to add HDUs at the end of the output
			FITS image describing each scan (default). Each scan
			will contribute an extra HDU at the end of the image.
			Disabling this option (e.g. via 'forget') can decrease
			the size of the output images, esp. for large data sets
			containing many scans.

:: write.scandata.details	@Advanced
				@Since 2.00-b2
				When the option is enabled, 'write.scandata'
			will add extra detail into the FITS outputs, such as
			channel gains, weights and flags, spectral filtering
			profiles and residual noise power spectra.
			@See: 'write.scandata'

:: write.spectrum[=<window>] 	@Expert
				Writes channel spectra (of residuals) into an 
			ASCII table. The optional argument can specify a window
			function to use. The available window functions are:
			'Rectangular', 'Hamming', 'Hann', 'Nutall', 'Blackman'
			'Blackman-Harris', 'Blackman-Nutall', and 'Flat top'.
			The default is 'Hamming'.
			The first column indicates the frequency, after which
			come the power-spectral-densities (PSD) of each channel
			used in the reduction (see 'noslim').
			@See: 'write.ascii', 'noslim'

:: write.spectrum.size=N	@Expert
				Specify the windowsize (in powers of 2) to use
			for measuring spectra. By default, the spectral range
			is set by the 1/f filtering timescale.
			@See: 'drifts'
