[daip] [!7399]: AIPS - Absolute flux calibration of old VLA data (c 2003) using 3C147

[Eric Greisen]

Eric Greisen updated #7399
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                 Due: - Cleared - (was: 09 October 2015 11:06 PM)

Absolute flux calibration of old VLA data (c 2003) using 3C147
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           Ticket ID: 7399
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/7399
           Full Name: Sara Beck
               Email: becksarac at gmail.com
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 06 October 2015 11:06 PM
             Updated: 09 October 2015 04:40 PM
      Resolution Due: 15 October 2015 11:06 PM (6d 6h 26m)



I had not replied to this query because I do not know what to say.

The flux and spectrum of 3C147 is well known.  You must run SETJY
with OPCODE 'CALC' to set the known, time-dependent fluxes vs
IF in the SU table.  Then, when you use the source model, the total
flux of the model is adjusted to match the values in the SU table.
I don't know what happens if you do not do the SETJY part - perhaps 
3C147 is adjusted to 1 Jy??

If you have done all this, then you could try using and not using the
source model which probably will not make a huge difference in the flux.
Do check that NORMALIZE is 0.0 in CALIB and the messages about scaling 
the model flux to match the SU table.

I also want to remind you that many sources change their flux at high frequency
by quite a lot over time.  So it is not clear what one should expect - the NRAO
calibration source list is reliable for the time  that the sources were observed
but not for some years before or since.  Do all of your sources appear to have
too much or too little flux?

Eric Greisen
 



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