[daip] [!5391]: aips - Extracting the values of error bars of closure phase

[Eric Greisen]

Eric Greisen updated #5391
--------------------------

       Staff (Owner): Eric Greisen (was: -- Unassigned --)
                 Due: - Cleared - (was: 27 August 2014 12:59 AM)

Extracting the values of error bars of closure phase
----------------------------------------------------

           Ticket ID: 5391
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/5391
           Full Name: JongHo Park
               Email: jhpark at astro.snu.ac.kr
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 25 August 2014 12:59 AM
             Updated: 25 August 2014 03:56 PM
      Resolution Due: 02 September 2014 12:59 AM (7d 9h 3m)



I have looked at the code for CLPLT and find that the computation
of error bars is completely wrong.  It was done back in the early 1990s
and shows a lack of understanding of the visibility data format.  It
assumes that the weights are correctly calibrated uncertainties in
the visibility, whereas the weights are in fact 1/uncertainty^2 if they
are in correct form at all.  Frequently weights are simply counters of
the number of data samples or some such and do not have the
correct units (1/Jy^2) and so cannot be used in this fashion.

I will correct CLPLT to use the weights properly in this computation
and also to add warnings in the help file.  I am not currently familiar
with how CLPLT works, but perhaps I can add a print option.

Eric Greisen




------------------------------------------------------
Staff CP:  https://help.nrao.edu/staff