[daip] Re: Radio imaging problem

[Eric Greisen]

Preeti Kharb writes:
 > Hi Eric,
 > 
 > Your suggested test works perfectly ! Thankyou
 > 
 > The way I tried bandwidth synthesis earlier was by first using the task
 > 'SPECR' (with NPOINTS=4) on the data, then DBCON and finally IMAGR with a
 > large number for NCHAV. However that result wasnt still as good as the one
 > I get after separating the IFs first, like you have suggested.
 > 
 > I am satisfied with the results I get using your method. But could you
 > please let me know if the way I did bandwidth synthesis was ok ?
 > 
The problem with all the ways that you did the imaging to begin with
is that AIPS just cannot keep track of all the frequencies.  The u,v,w
are in wavelengths and it assumes that the ratio of IF2 to IF1 in the
first data set is that of the second.  In your case those ratios were
grossly different.  You had ~ +30% different frequencies in the A array
observations and ~ -10% in the other case.

You could split the SPECR outputs into separate IFs, join them with
DBCON and probably do even better.

Eric Greisen