[daip] [!5320]: aips - OMFIT

[Eric Greisen]

Eric Greisen updated #5320
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       Staff (Owner): Eric Greisen (was: -- Unassigned --)
                 Due: - Cleared - (was: 07 August 2014 06:18 PM)

OMFIT
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           Ticket ID: 5320
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/5320
           Full Name: Lynn D Matthews
               Email: lmatthew at haystack.mit.edu
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 05 August 2014 06:18 PM
             Updated: 06 August 2014 05:18 PM
      Resolution Due: 13 August 2014 06:18 PM (7d 1h 0m)



It is modestly supported.  But why are you not averaging the data 
in frequency even more?  It does not fit spectral index and really
only does continuum except for maser lines.  If your source varies
a lot from channel to channel in the visibility, then spectral index
is too important to be ignored.

I suspect that too much data just makes for more degrees of freedom
and hence more ways for OMFIT to fail.  It does well when the initial
guess and data are close, not otherwise.  The task is fragile in that
sense (as CUBIT is in rotating galaxy models).

The data are stored on disk so there should be no limit.  A quick glance
did not reveal to me whether the modeling code takes frequencies into
account correctly (or at all).

eric




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