[daip] VLA+Pt Calibration Problem

[Jim Ulvestad]

Hi Emma,

I guess I'm confused at the moment over what your problem is.
It is quite normal to calibrate 3C 286 or 3C 48 without using all
the antennas.  What you really need is the flux density of your
secondary calibrator, namely the one you use to calibrate your
source.  This in no way requires a 3C 286 calibration using Pie Town.
In fact, it only requires a subset of VLA antennas, possibly
as few as 6 or 9 antennas.

All you have to do is the normal VLA calibration process.

STEP 0: Set the flux for 3C 286 using SETJY

STEP 1: Use CALIB to solve for 3C 286 gains using the uv range
specified in the calibrator manual.  The fact that you have no solution
for PT here is COMPLETELY IRRELEVANT.  The solutions
for this will be written into SN table 1.

STEP 2: Run CALIB again on 1727+455 using all antennas, and the
uv minimum of 6 kilolambda specified in the calibrator manual.
This should give you a good solution for Pie Town relative to the other
antennas, which will be written into SN table 2.

STEP 3: Run GETJY with CALSOUR=3c286 and sour=1727+455
to get the flux density of 1727+455, which will be automatically
computed and entered into the source table.

 From here on, all you need to do is use 1727+455 to calibrate your
target source.  I'm not sure what your observation is--maybe you have
other calibrators for which you need fluxes, or maybe you have only
one calibrator and one target that you observe repeatedly.  But if
all you have is 1727+455 plus a nearby target, all you need to do
now is run CLCAL with CALSOUR=1727+455, SOUR=target,
and SNVER=2, and you're basically done.

It is possible that I don't understand what your observation was,
and this is causing me to miss something.  If you are trying to
calibrate polarization position angle, for example, and use 3C 286
for that, it will get trickier toward the end.

Best,

Jim Ulvestad



Emma Rigby wrote:

>On Wed, 13 Jul 2005, Eric Greisen wrote:
>
>  
>
>>That uvrange should leave PT out entirely I would have thought.  3C286
>>is just too extended for such baselines.  The curiosity is why the
>>other data set worked - perhaps other calibration sources?
>>
>>We are working on models for 3C286 and the other 3 main flux cals but
>>have not yet reached L band.  These models come with aips and use verb
>>CALDIR to tell you which are currently available.  With the models one
>>can calibrate much better than with uvrange.
>>
>>Eric Greisen
>>
>>    
>>
>
>Yes, there are other calibration sources (1727+455 for this data set) so I
>think you're right about the other data. Would it be appropriate to use
>one of the models for the other bands for the calibration?
>
>Thanks again
>Emma Rigby
>
>
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