Spots

[Dr. Frank W. Jenichen]

Posted to CCD-world:
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Tom Droege schrieb:

> Posted to CCD-world:
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> The Amateur Sky Survey now has several 2k x 2k CCD cameras running
> using
> the CCD442A.  We have bought the Grade 4 (lowest cost) devices.
>
> On one of the cameras, I see large round dark spots.  One is a few
> hundred
> pixels in diameter.  Others are smaller.  Most of these spots
> represent
> lower sensitivity of a few percent.  One has increased sensitivity.
> Being
> the tass list, these have sparked a debate as to their source.  We are
>
> running the present CCDs with covers.  (CCDs are now on order without
> covers.)  In my opinion, the edges of the spots are too sharp to be
> due to
> dirt on the cover or in the optics.  The spots are on the only CCD
> with a
> bad column, indicating that this is possibly a lower grade overall
> device.
>
> Can anyone tell me if such spots are common on a CCD?

Not at all. I think You should use better CCD grade if possible. We
normally use best grade CCD and dont have similar problems.

> Flat fielding mostly
> removes the problem, so this in not all that serious a defect.
>
> Tom Droege
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> For information about CCD-world, send email to
> owner-CCD-world at cfht.hawaii.edu.


greetings
--
Frank Jenichen
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