Subject: bias values vary with rotator position

From: richmond@astro.Princeton.EDU

Submitted: Sat, 18 May 1996 15:35:33 -0400 (EDT)

Message number: 39 (previous: 38, next: 40 up: Index)

  I'm now reducing some DSC data taken Apr 18/19, 1996.
Looking at the values in the over-scan and pre-scan
areas at the edges of the chip, I see a variation of about
50 counts between frames taken at "normal" rotator position,
and those taken after rotation by 90 degrees.  The difference
occurs several times during an observing session, always
in the same sense.

  And, of course, the bias varies when the DSC is taken
on/off the telescope (by about the same amount, 50-60 counts).

                         Michael Richmond
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