[daip] [!8277]: AIPS - Self-cal using SCMAP

[Eric Greisen]

Eric Greisen updated #8277
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                 Due: - Cleared - (was: 19 April 2016 12:30 AM)

Self-cal using SCMAP
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           Ticket ID: 8277
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/8277
           Full Name: Alexandra Truebenbach
               Email: alexandra.truebenbach at colorado.edu
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 13 April 2016 07:46 PM
             Updated: 15 April 2016 07:57 PM
      Resolution Due: 21 April 2016 07:46 PM (5d 23h 49m)



VLBI users sometimes use difmap but I have no experience with it.

I want to warn you about self-cal and coordinates.  Once you have done any self-cal
the accuracy of the coordinates is compromised - your initial calibration must be very
good or self-cal can move the sources around rather badly.  I hit this on old VLA
data where we had 2 5-minute snapshots and bad phases.  We started with an NVSS
model - so pretty good - but self-cal moved the strongest component at our freq
(P band) to the strongest at L and ignored the fact that the other, comparable,  
components did not line up at all.  Be careful of your initial calibration and check
that sources are not moved much.

Good luck

Eric Greisen




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