[daip] MAXFIT recommend shifts.

[Craig Walker]

I made a typo in specifying the offset field center for a second field 
on a possible second source in the VLBA 6cm image I'm currently making.
I specified an RASHIFT of -1.399 arcseconds when the shift I had 
calculated from coordinates in the literature was -1.339 arcseconds.
I think I have detected the source and ran MAXFIT (from TVMAXFIT) on it.
The peak is in X pixel 308 in a 1024 image.  That is offset from the 
center by 204 pixels with a 0.0003 cell size, or 0.0612, which is very 
close to what the typo would give me.

MAXFIT then recommends an RASHIFT of -1.398854 arc seconds to center
on the pixel.  That is what I used so it is not going to center the 
source.  It is as if MAXFIT is giving the offset needed to center the
reference pixel of the offset image - ie not really shift from where it 
is already.  I had presumed that the recommended shifts would be
meant to center the source.  Am I misunderstanding something, or is 
MAXFIT getting it wrong?

The offset image is on noatak user 332  J1502S.ICL002.1004  The source
at 307,499 is the one measured.  It is very weak so I am working on
establishing its reality.

Cheers,

Craig

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     R. Craig Walker            Array Operations Center
     cwalker at nrao.edu           National Radio Astronomy Observatory
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