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2 GAIN

This is the gain of the subtraction loop.  It should typically be chosen in
the range 0.05 and 0.3.  Higher values give faster convergence, while lower
values give a better restitution of the extended structure. A sensible
default is 0.2.

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2 NITER

This is the maximum number of components the program will accept to
subtract.  Once it has been reached, the program starts the restoration
phase.

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2 FRES

This is the minimal fraction of the peak flux in the dirty map that the
program will consider as significant.  Alternatively, an absolute threshold
can be specified using ARES.  Once this level has been reached the program
stops subtracting, and starts the restoration phase.  This parameter is
normalized to 1 (neither in % nor in db).  It should usually be of the
order of magnitude of the inverse of the expected dynamic range of the
intensity.

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2 ARES

This is the minimal flux in the dirty map that the program will consider as
significant.  Alternatively, the threshold can be specified as a fraction
of the peak flux using FRES.  Once this level has been reached the program
stops subtracting, and starts the restoration phase.  The unit for this
parameter is the map unit (Typically Jy/Beam).  The parameter should
usually be of the order of magnitude of the expected noise in the clean
map.

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2 BLC

These are the (pixel) coordinates of the Bottom Left Corner of the cleaning
box.  The actual cleaning support will be the intersection of the specified
window with the inner quarter of the map and with any user defined polygon.

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2 TRC

These are the (pixel) coordinates of the Top Right Corner of the cleaning
box.  The actual cleaning window will be the intersection of the specified
window with the inner quarter of the map and with any user defined polygon.

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2 POSITIVE

The minimum number of positive components before negative ones are
selected.

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2 KEEP

This is a logical flag to keep cleaning after an approximate convergence
has been reached.  It should usually be set to .TRUE., except may be for
the SIMPLE method.

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2 MAJOR

This is the major axis (FWHP) in user coordinates of the Gaussian restoring
beam. If 0, the program will fit a Gaussian to the dirty beam. We strongly
discourage to change the default value of 0.

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2 MINOR

This is the minor axis (FWHP) in user coordinates of the Gaussian restoring
beam. If 0, the program will fit a Gaussian to the dirty beam. We strongly
discourage to change the default value of 0.

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2 ANGLE

This is the position angle (from North towards East, i.e. anticlockwise) of
the major axis of the Gaussian restoring beam (in degrees).  If 0, the
program will fit a Gaussian to the dirty beam. We strongly discourage to
change the default value of 0.

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2 BEAM__PATCH

The dirty beam patch to be used for the minor cycles in CLARK and MRC
method.  It should be large enough to avoid doing too many major cycles,
but has practically no influence on the result.  This size should be
specified in pixel units.  Reasonable values are between N/8 and N/4, where
N is the number of map pixels in the same dimension.  If set to N, the
CLARK algorithm becomes identical to the SIMPLE algorithm.
