[daip] bandpass calibration

[Neal Miller]

Hi.

This email is related to the earlier ones about differences
I was noting in calibration on a new machine with 31DEC07
aips vs. an older one with 31DEC06.

Something is definitely different in the bandpass calibration.
I've attached a pair of plots generated with POSSM, for the
BP table generated on the 31DEC06 system (narya) and the one
for the 31DEC07 system (nenya). The shapes and phases are
identical, but the amplitude scales differ for some reason.
I did the same exercise using a 31DEC04 installation (also on
narya) and the bandpass looked the same as those from the 31DEC06.
Since the shapes are the same, I'd expect that this would just
be corrected out when doing the flux calibration - however,
it would seem useful to understand why this difference is
occuring. It is a potentially useful lead, since the bandpass
calibration occurs very early in the reductions and there
are only a few precursor steps to investigate.

Neal
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