[daip] SDCLN and additional questions

[Rene Giessuebel]

Hello,

sorry in advance if some questions might be a bit stupid, this is my
first try reducing interferometry data.
I have VLA data (C-Band, D configuration) of an extended source. I want
to clean the image using the task SDCLN
I get the following error:

pc2001> SDCLN1: BMSHP ERROR: CENTER OF BEAM =  0.49187E-04

Could you please explain to me what it means (what is the problem), and
how I can fix it?
The map-file I used was created using IMAGR with NITER 0

I tried to use UVMAP as described in the help/explain of SDCLN, but it
complained:
pc2001> UVMAP1: ERROR: I cannot process packed UV data, use SPLIT
even after using SPLIT ... I tried to do self-calibration and did some
additional flagging on the "initial" split-file, so I want to use that
one ... or is that the cause?

Or would you advise to use IMAGR for SDI Clean anyway?

Also I did not fully understand how to use cleaning boxes. Some people
say to use boxes as small as possible around the point-sources, others
advise to use big boxes and claim that small boxes somehow bias the
cleaning towards small structures(?)
Anyway, I played around a bit and found that I get the best results by
arbitrarily setting rather big boxes around the region I want to clean
next, starting around a couple of brighter sources and always selecting
around the strongest sources I see in the residual ... so it still is a
semi-structured way of doing it, but seems "wrong" to me.
Any advise on where I can read up on why and how to use boxes? I am
really confused with all the different types of boxes and fieldsizes one
can define for cleaning actually ... and what does NBOXES do when I set
more then one box in the TV?

Another question I have concerns subtraction of sources.
I have a source in the north of the image which produces beautiful but
unwanted patterns over bif parts of the image even after cleaning.
I tried to remove the source from the UV-file, but the method I found
requires a good model from the cleaning-components. But if I had good
CC for that source, I obviously wouldn't want to remove it ... ;-)
Is there another way?
Would it be worthwhile doing self-calibration on this source only just
to remove it, and then use these CC to remove it from an UV-file with
"normal" calibration? I don't have really strong sources (strong as in
"good for selfcal") though, so selfcal probably doesn't do much anyway.

Thanks in advance,
René Gießübel
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René Gießübel                                  rgiess at mpifr-bonn.mpg.de
Max-Planck-Institut für Radioastronomie        room:               2.09
Auf dem Hügel 69                               phone:   +49 228 525 314
53121 Bonn
Germany                 http://www.mpifr-bonn.mpg.de/staff/rgiessuebel/
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