[daip] AIPS Query

[Eric Greisen]

dbgob at brandeis.edu writes:

 > 1.) I tried using CLIP and CLIPM. CLIP does not let me select a source  
 > and seems to work on all sources, creating a CLIP file, but seems to  
 > not have flagged data. When I used CLIPM I gave it parameters based on  
 > uncalibrated data I wanted to flag but no matter what inputs I give it  
 > (only gave it min/max for parallel/cross) it seems to flag everything.  
 > Ideas?

       Not without a LOT more information.  Your inputs to CLIPM would
be helpful as would a sample of the output.  If you have applied
calibration then the clip limits had best be set for calibrated data
or vice versa.

 > 
 > 2.) Recently we have started to work with BLCAL in the office. This  
 > works great for a strong source like 3C48 and so I wanted to take it  
 > to data sets with just pointy phase calibrators. I choose a set I was  
 > working on recently which had data washed out by symmetry noise from  
 > the array. I calibrated my data, read it out of AIPS, cleaned and  
 > selfcaled the phase calibrator in Difmap, then brought the fits file  
 > back into AIPS, and used it as the model for BLCAL on the phase  
 > calibrator. The manual says I need at least 100:1 to do this and by my  
 > estimates this source has 3000:1 and should work fine. Splitting off  
 > the primary source using my new BL table I was able to get rid of the  
 > noise that was pestering me before, but I am troubled that the UV plot  
 > looks very distorted. Have I done something wrong? Is my source  
 > fidelity not good enough? Improper use of the task?

Again "very distorted" covers a multitude of evils.  Try dividing your
calibrated data by your model with UVSUB and plotting the result.  The
BLCAL help file says that the amplitudes should be 1.0 and phases 0.0
or nearly so.

What version of AIPS are you running (version code 31DEC0? and last
update date)?  BLCAL was in need of a lot of repair in the fairly
recent past and CLIPM was renamed CLIP not too long ago.

Eric Greisen