[daip] Source correction with CLCOR

[Eric Greisen]

Andrew Biggs wrote:
> Hi Eric. I have a question about CLCOR versus UVFIX. CLCOR seems to have
> worked well for the phase calibrator, where the the position shift was
> only a few mas. I also shifted the target, but by nearly an arcsec. The
> resultant map of the target was pretty awful and I suspect that this is
> because the shift was too large. I repeated the calibration without the
> target CLCOR shift and instead ran UVFIX after all the calibration steps
> had been carried out. This map looks absolutely fine. So, I think that
> this is entirely expected behaviour, but just wanted to check with you.
>
CLCOR does good phase corrections but does not re-compute u,v,w

A large change in coordinate requires a recomputation of u,v,w.  I 
suspect that doing the shift with CLCOR but then running UVFIX to do the 
re-computation would work as well as doing the shift in UVFIX.  Note - 
CLCOR used to be better than UVFIX for the phases but I improved UVFIX.

Eric Greisen