Re: Post flat processing

[Chris Albertson <chris@topdog.pas1.logicon.com>]

aah@nofs.navy.mil wrote (in part):


> (1) I hope that this processing will be used *only* for already acquired
>     data.  The far better approach in the future is to use a flatfielding
>     system that doesn't need corrections.

What is the rate of change of flat fields?  What makes them change?  Dirt
on the lens?  Do we know?  It seems that if you could take a good flat with 
a flat field device known good to <<1% then if the rate of change were close to
zero then you could simply apply the known good flat retroactively.  Trouble
is I don't think we know if the rate of change of flat fields is near zero
of not.

It seems to me that even if Mike's proposed method has systematic errors
it would still be a very good way to determine if the flat field remains
constant over an extended period.  It it is determine that the FF is
constant then we can do with only one flat field device that is mailed
between the Mk III sites.



--Chris Albertson

  chris@topdog.logicon.com                Voice:  626-351-0089  X127
  Logicon RDA, Pasadena California          Fax:  626-351-0699