[daip] calib flagging and imaging loops.

[Craig Walker]

If you use the flagging facility now in CALIB, I believe there is a 
gotcha for the way I do imaging loops.  CALIB writes a flag table each 
time.  In that table, it puts whatever was in table FLAGVER (or the 
highest if FLAGVER=0), plus the new flags.  For the imaging loop, I keep 
going back to the same input file and I have traditionally used 
FLAGVER=0.  As a result, that file acquires a large number of flag files 
containing all the flags from all the runs of CALIB.  I believe that, if 
you use FLAGVER < 0 so the flags are not applied, and you have not done 
any real flagging using flag tables, this is benign.  It might also be 
benign if you force FLAGVER=1 or some other value for a table that 
contains desired edits.  But if in blissful ignorance (ie, I did it), 
you leave FLAGVER=0, you slowly whittle away your data, which is not 
really what you want.  I see now that a careful reading of the help file 
explains what will happen.  But perhaps a more explicit warning about 
the consequences of using FLAGVER=0 and sequential CALIBS on the same 
file would save others the same grief that I just had.

Cheers,

Craig

---------------------------------------------------------------------
     R. Craig Walker            Array Operations Center
     cwalker at nrao.edu           National Radio Astronomy Observatory
     Phone  505 835 7247        P. O. Box O
     Fax    505 835 7027        Socorro NM 87801   USA
---------------------------------------------------------------------