[daip] 3C 48 model

[Jim Ulvestad]

Hi Amy,

I'm just working at archival data, which typically is observed
at the X-band defaults.

Frequency Table summary
FQID IF#      Freq(GHz)      BW(kHz)   Ch.Sep(kHz)  Sideband
   1   1       8.43510000   50000.0039  50000.0039      1
       2       8.48510000   50000.0039  50000.0039      1

Best,

Jim

> Hi Jim,
>
> Well, there is a strongish confusing source to the north of the 3C48 so
> that
> might have something to do with it.  What frequency (exactly) did you
> observe
> at?  I think this is the first model I made, so I may have put it together
> wrong.
>
> Amy
>
> Jim Ulvestad wrote:
>> Hi Amy et al.,
>>
>> I'm reducing a data set from 2002, A configuration, X band,
>> with 3C 48 as the only flux calibrator, using VLACALIB.
>> VLACALIB is clearly picking up the model, as I get a new
>> image/CC file for 3C 48 showing up in my directory every
>> time I run it.
>>
>> But I'm getting many amplitude closure errors in the 10-20%
>> range, concentrated in the antennas on the North arm.
>> The source was not observed exactly at transit, but about
>> 2.25 hours from transit.  There is an adjacent calibrator
>> at 0151+277 (4 deg. away in RA, 6 deg. in dec.), observed
>> 5 minutes apart, that shows no errors at all, leading me
>> to believe this shouldn't be atmosphere.  Over a 3.5
>> minute scan, the phases do reasonably well, wrapping up
>> to 30-40 deg. on some baselines, more typically 20 deg.
>> or so.
>>
>> I can't find any bad data in LISTR, though I will look
>> a little bit more.
>>
>> Yes, I did run SETJY first.
>>
>> So my question is, have you typically seen this level of
>> amplitude closure problems on 3C 48 even with your model?
>> I recall that X-band A array used to be a kind of bad
>> circumstance to use 3C 48 in; the calibrator manual says
>> to use only the inner 2 antennas.  Is it possible that the
>> source has enough structure that the model just doesn't do
>> well enough?
>>
>> Thanks,
>>
>> Jim
>>
>>
>>
>> _______________________________________________
>> Daip mailing list
>> Daip at listmgr.cv.nrao.edu
>> http://listmgr.cv.nrao.edu/mailman/listinfo/daip
>>
>