RE: Star's magnitude adjustments

[aah@nofs.navy.mil]

Mike G. gave a description of his magnitude adjustment scheme.  Sounds
fine on the surface.  A couple of questions:
  If you have 8 regions, then there are 8 'constants' that are used for
the adjustment?  That is, each region uses a single value for its
adjustment and does not include a slope parameter?  Doesn't this cause
a discontinuity at the border between the regions?  Why not use something
like a quadratic/cubic/cubic spline instead and have it valid over the
entire image?
  The original flat vector is created from some nearby (in time) photometric
night?  How often do you update the flat vector?  How do you handle a
change in the flat vector (such as monitoring it to see when changes occur)?
  How many outliers are removed for a typical adjustment calculation?  Is
it a significant number compared to the ones left in the calculation?
  You mentioned earlier that you get different adjustments on a nightly
basis.  This sounds wrong to me.  Once the flatfield has been calculated,
a single adjustment should modify it sufficiently to make it 'flat'.  If
you find a night-to-night variation in this adjustment, then I don't
understand what is happening.
Arne