[daip] Error in AIPS task FILLM in handling opacities

[gcastell at iafe.uba.ar]

Dear Amy,

thank you very much for answering. I am worry because I was not able to
get the right flux density at any of the frequencies yet (I mean at 74 and
330  MHz). I don't know what it's wrong with the self-calibration
procedure. Of course, it's a good news that fillm had worked ok in my
case.

thanks
cheers,
gabi

> Dear Gabi,
>
> Since you are doing low frequency it should not effect you, I guess
> "relatively
> high frequency" should have been defined more quantitatively.
>
> Amy
>
> gcastell at iafe.uba.ar wrote:
>> Dear AIPS's people,
>>
>> I am writing to you concerning a warning on the 31DEC08 version of FILLM
>> that I received via email several days ago.
>> Nowadays, I am reducing continuum data taken in direction to the
>> supernova
>> remnant IC443.
>> The observations were carried out in a dual mode at 74 and 330 MHz. My
>> question is: Should I be careful with some problem in FILLM?
>> I think my situation is diferent from that you described in the email,
>> but
>> I am not completely sure about it.
>>
>> I will be very grateful if you could tell me something about problems in
>> the task FILLM  when observations are made in dual mode.
>>
>> thank you very much in advance,
>> Best Regards,
>> Gabi
>>
>>
>>> To: All VLA users
>>> Subject: Error in AIPS task FILLM in handling opacities
>>>
>>> Dear colleague,
>>>
>>> The 31DEC08 (TST) version of FILLM had a problem with its handling of a
>> newly available band code in an observation.  In the period from
>> September
>>> 13 to October 20, 2008, FILLM was under the impression that the data it
>> was handling were in the band of the new scan rather than the band of
>> the
>>> scan it still had to finish writing.  If your observations were all at
>> one band, then there is no problem.  If there were band changes during
>> the
>> observation then the last record of each scan in CL table version 1 will
>> have opacities and antenna gains calculated for the (incorrect) band of
>> the next scan.  This can make a significant error if one of the bands is
>> at relatively high frequency.  This error can be repaired most simply by
>> deleting all CL tables including version 1 and running INDXR, or it can
>> be
>> repaired by using a version of FILLM from a midnight job run after
>> October
>> 20, 2008.
>>> Please contact daip at nrao.edu if you have any further questions about
>>> the
>> quality of your data.
>>> Claire Chandler
>>> Deputy Assistant Director for Science, NM Operations
>>> _______________________________________________
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>>>
>>
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>