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: http://www.atnf.csiro.au/computing/software/miriad/doc/clean.html
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Task: clean Purpose: Apply Hogbom, Clark or Steer CLEAN algorithm to a map Categories: deconvolution CLEAN is a MIRIAD task that performs a hybrid Hogbom/Clark/Steer Clean algorithm, which takes a dirty map and beam, and produces an output map which consists of the Clean components. This output can be input to SELFCAL to self-calibrate visibilities, or input to RESTOR to produce a "clean" image. Optionally CLEAN can take as one of its inputs a model of the deconvolved image. This model could be from a previous CLEAN run, or from other deconvolution tasks (e.g. MAXEN). Key: map The input dirty map, which should have units of Jy/beam. No default. Key: beam The input dirty beam. No default Key: model An initial model of the deconvolved image. This could be the output from a previous run of CLEAN, or the output of any of the deconvolution tasks (e.g. MAXEN). It must have flux units of Jy/pixel. The default is no model (i.e. a zero map). Key: out The name of the output map. The units of the output will be Jy/pixel. This file will contain the contribution of the input model. It also should have a different name to the input model (if any). It can be input to RESTOR, CLEAN (as a model, to do more cleaning), or SELFCAL (for self-calibrating visibility data). Key: gain The minor iteration loop gain. Default is 0.1. Key: options Extra processing options. Several can be given, separated by commas. Minimum match is used. Possible values are: negstop Stop when the first negative component is encounterd. This does not apply when using Steer iterations. positive Apply a positivity constraint. This constrains the component image to be non-negative. A side-effect of this is that CLEAN will stop iterating if it cannot continue to ensure this. This does not apply when using Steer iterations. asym The beam is asymmetric. By default CLEAN assumes the beam has a 180 degree rotation symmetry, which is the norm for beams in radio-astronomy. pad Double the beam size by padding it with zeros. This will give you better stability with Clark and Steer modes if you are daring enough to CLEAN an area more than half the size (in each dimension) of the dirty beam. Key: cutoff CLEAN finishes either when the absolute maximum residual falls below CUTOFF, or when the criteria described below is satisfied. The default CUTOFF is 0. Key: niters The maximum number of minor iterations. The default is 250, which is too small for all but the simplest of images. CLEAN will stop when either the maximum number of iterations is performed, or the cutoff (see above) is reached, or if options=negstop was given and a negative component was found, or if options=positive was given, and no more positive components could be found. Key: region This specifies the region to be Cleaned. See the help on region for more information. The default is the largest region that can be deconvolved safely. Key: phat Cornwell's Prussian helmet parameter. When cleaning extended sources, CLEAN may produce a badly corrugated image. This can be suppressed to some extent by cleaning with a dirty beam which has had a spike added at its center (i.e. a beam that looks like a Prussian helmet). PHAT gives the value of this spike, with 0 to 0.5 being good values. Default is 0 (but use a non-zero value for extended sources). Key: minpatch The minimum patch size when performing minor iterations, in pixels. Default is 51, but make this larger if you are having problems with corrugations. You can make it smaller when cleaning images which consist of a pretty good dirty beam. Key: speed This is the same as the speed-up factor in the AIPS APCLN. Negative values makes the rule used to end a major iteration more conservative. This causes fewer components to be found during a major iteration, and so should improve the quality of the Clean algorithm. Usually this will not be needed unless you are having problems with corrugations. A positive value can be useful when cleaning simple point-like sources. Default is 0. Key: mode This can be either "hogbom", "clark", "steer" or "any", and determines the Clean algorithm used. If the mode is "any", then CLEAN determines which is the best algorithm to use. The default is "any". Key: clip This sets the relative clip level in Steer mode. Values are typically 0.75 to 0.9. The default is image dependent. Revision: 1.14, 2015/10/29 01:31:02 UTC