Star's magnitude adjustments

[aah@nofs.navy.mil]

  The correction vector to the flatfield vector should be either included
in the flatfield vector itself and used to reprocess the data, or included
in the 'instrumental magnitude'.  A single zero point adjustment per frame
should be all that is reported to the database.  The correction vector 
(or flat compensation in Mike's terminology) is
just another calibration step to get good instrumental magnitudes and is
no more likely to be 'backed out' than is the flatfield itself.
  I would like some more information about the flat compensation program
when it is available, namely how you are determining this correction for
non-photometric nights, what kind of fit you are using, the number of
stars used to determine the fit, a handle on the fit error, etc.  There is
always the potential of making a systematic error in applying such a
correction, so we should check it *very* carefully before using it in
a production mode.
Arne