[daip] question with CLCAL

[Eric Greisen]

Jacob Eggers writes:
 > Hi,
 > 
 > I'm working at the Brandeis Astrophysics lab this summer and I had a 
 > question about the CLCAL task. I'm unclear on how exactly to specify the 
 > calsour and sour.

     In general, you want to calibrate all sources, i.e. SOUR=' '
with all the calibrators in the SN table(s).  Some users prefer to
restrict calibrations so that one calibrator source is applied to a
specific list of sources and another cal to another list of sources.
It depends on how the observations were done.

 > Do I calibrate the source with both calibrators, or just the 
 > primary calibrator?

Not knowing the observation sequence or what you mean by these terms
it is hard to answer this question.  In general, one observes certain
basic calibrators (3C48, 3C286, etc) which are the primary flux
calibrators and then one observes much more often with a weaker,
probably flux variable cal source near the target source.  Sometimes
one wnts to apply only that - actually secondary - cal to the target
although it usually does not matter if you apply all cals.

 > 
 > And, do I also self-calibrate the calibrators?

Modern copies of aips provide models for the 4 primary flux
calibration sources at some of the VLA frequencies.  Enter the verb
CALDIR to see which are available to you.  If you observed one or more
of these sources at the provided frequency bands, then you should use
CALRD to read in the model.  Then run CALIB for that cal source alone
providing the model in IN2NAME et al. with NMAPS=1.  Note that you do
this before running GETJY.

Eric Greisen