[daip] [!4188]: aips - blanking in GBT maps

[Trisha L Ashley]

Trisha L Ashley updated #4188
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blanking in GBT maps
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           Ticket ID: 4188
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/4188
           Full Name: Trisha L Ashley
               Email: trisha.ashley at gmail.com
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: ALMA E2E
      Template Group: Default
             Created: 22 December 2013 08:47 PM
             Updated: 22 December 2013 08:47 PM
                 Due: 25 December 2013 12:00 AM (2d 3h 13m)
      Resolution Due: 01 January 2014 12:00 AM (9d 3h 13m)



Hello,
I am having a problem with AIPS blanking my GBT data: 
I first noticed the problem in XMOM; I tried to set FLUX and ICUT so that the entire range of my data was included in the final maps (both set to about -10000000) and I kept getting maps that are mostly blanked.  I tried to prevent this by setting OPTYPE to 'NBIV', but I was still getting blanked maps.  The FLUX setting appeared to be the problem so I tried many different numbers for FLUX.   The results from this test were that the maps began to be blanked at -0.02 (Kelvin).  Anything more negative than this value led to more blanked pixels and anything more positive than -0.01 had no blanked pixels.  
This led me to look at the SDGRD cube and I noticed that this cube had "Magic value blanking" in the header.  I looked at the explain file for SDGRD and found that the only place it mentions blanking is in the REWEIGHT parameter.  However, I have this set to 0 0 which, as far as I can tell should not blank pixels in the cube.  
So I am still unsure as to where the pixels are being blanked; I have only used DBCON, SDGRD, TRANS, and XMOM on the data.  Any help in understanding this would be greatly appreciated.  I am mainly concerned that any flux measurements I try to make will be incorrect.  
The SDGRD parameters that I have set are:
OPTYPE     '-GLS'  
APARM   8  56  36.9502  68  4  57.576 
IMSIZE       40          40
CELLSIZE    210         210   
REWEIGHT      0           0  
xtype -16
ytype -16
XPARM       550  275  462   2    
YPARM       550  275  462   2    

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