[daip] Re: Problem with UVFIX

[Eric Greisen]

Preeti Kharb writes:

 > I was wondering if you could help me with this UVFIX problem I am facing.
 > 
 > I had used DBCON to add 3 VLA uvdatasets and for some cases I have
 > mistakenly kept DOARRAY=1, instead of -1. The 3 datasets used VLA A,B & C
 > arrays at a particular frequency and were observed at different dates.
 > 
 > I had then used the resultant DBCON file to make the maps, after doing a
 > couple of IMAGR+CALIB rounds and obtained OK final maps.
 > 
 > Now I am trying to use UVFIX on the final CALIB files which I got after
 > all the selfcals, to shift the position of the source by, say, 0.2".
 > 
 > This is messing up the uvdatasets. When I examine with UVPLT, I find that
 > the uvdata for all the individual arrays is not coincident anymore, like
 > it was before, but spread all over.
 > 
 > This problem does not arise for CALIB files got with DBCON, DOARRAY=-1.
 > 
 > So I want to know if there is some way I can rectify the problem, like
 > split the data again into subarrays and then try UVFIX ?

     The problem I suspect is that you have lost the antenna file(s)
that are discarded when DOARRAY=+1.  Thus it knows the correct time
but not the station locations.  Note that IMAGR with DO3D=1 will do a
good job with a large shift without UVFIX.

Eric Greisen

 > 
 > I tried running the task USUBA and also VLBASUBS, but each time I got this
 > message:
 > 
 > COLLIE> USUBA1: Determining subarray assignments automatically
 > COLLIE> USUBA1: SUBID: PARAMETER MAXENT TOO SMALL. CONTACT AIPS ADMIN.
 > COLLIE> USUBA1: Purports to die of UNNATURAL causes
 > 
 > Can you please advise ?
 > 
 > Thanks
 > 
 > Preeti
 > 
 > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 > Preeti Kharb
 > Postdoctoral Fellow
 > 76-3116, Centre for Imaging Science
 > Rochester Institute of Technology
 > 54 Lomb Memorial Drive, Rochester, NY 14623
 > Tel: 1.585.475.5665     Fax: 1.585.475.4153
 > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=