[ Basic Info | References | User Guide ]
Basic Information on tvcln
Task: tvcln
Purpose: Clark/Steer CLEAN with display of intermediates
Categories: deconvolution
TVCLN is a MIRIAD task, which performs a hybrid 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 any of the 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. It can be input to RESTOR, CLEAN (as a model, to do
more cleaning), or to SELFCAL (for self-calibrating visibility
data).
Key: gain
The minor iteration loop gain. Default is 0.1.
Key: cutoff
CLEAN finishes when the absolute maximum residual falls below
CUTOFF. Default is 0.
Key: niters
The maximum number of minor iterations. Clean finishes when
abs(NITERS) minor iterations have been performed. Clean may finish
before this point, however, if NITERS is negative and the absolute
maximum residual becomes negative valued, or if the cutoff level
(as described above) is reached.
Key: region
This specifies the region to be Cleaned. The default is the largest,
centered region that it is safe to deconvolve.
Key: phat
Cornwells prussian hat 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 hat).
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. 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 less 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 a Steer clean, values
typically being 0.75 to 0.9. The default is image dependent.
Key: server
If this is set to the name of a TV device, then at the end of
each major cycle, the restored image is displayed on the TV.