[daip] [!12819]: AIPS - FITLD DOWEIGHT seems to affect visibility amplitudes as well as weights

[Eric Greisen]

Eric Greisen updated #12819
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              Status: Closed (was: Open)
           Reply due: - Cleared - (was: 23 October 2018 05:53 AM)

FITLD DOWEIGHT seems to affect visibility amplitudes as well as weights
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           Ticket ID: 12819
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/12819
                Name: Michael Bietenholz
       Email address: mbieten at yorku.ca
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Closed
            Priority: Default
      Template group: Default
             Created: 18 October 2018 11:27 AM
             Updated: 19 October 2018 02:56 PM

The code uses the current BW and int time so if they changethen the relative weights will change.  It should normally beessentially constant so that the relative weights depend onthe quality of the correlation alone.  Walter has said that hewill look at the question I brought up.  The code suggeststhat modern VLBA data and all other FITS-IDI data should havethe amplitudes divided by the integration time.  But, recentVLBA IDI files do not contain the keyword that would makethem "recent".  Given that amplitude cal in VLB comes fromTsys rather than cal sources, any change in the initialscaling directly affects the amplitudes after cal.  I have 2data sets with different int times but cannot determine if one should have been divided by 4.CheersEric


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