CCD-world: dark signal

[Klaus Reif]

The following was posted to CCD-world:

>I have sent my previous question because I have found that the dark noise
>follow a linear relationship to the mean dark level istead of a square root
>(the normal Poisson statistics). I have tested 2 standard CCD sensors and 1
>MPP at room temperature and at -20°C
>
If the noise goes linear with the dark signal level you
probably see random pixel-pixel variations of the dark
electron production rate. This noise may be 10%  
of the signal level or more. Usually it dominates completely any 
other noise contribution. But this random pattern is stable.
You may remove it by subtracting dark exposures with 
identical exposure time, like Tim Hardy already mentioned. 
The resulting noise is the Poisson-noise*SQRT(2) of an
individual dark exposure.

Klaus Reif
*******************************************************************
Klaus Reif
Sternwarte of the Univ. of Bonn                 Phone:    +49 228 737834
Auf dem Huegel 71                                   FAX:     +49 228 733672
D 53121 Bonn                                          Email:
reif at astro.uni-bonn.de
Germany                                                   WWW:
http://www.astro.uni-bonn.de/~reif
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