CCD-world: dark signal

[Bruce Atwood]

The following was posted to CCD-world:

You have pixel to pixel variation in your dark current.  If you really
have the device in the dark and at constant temperature you can take
PAIRS of exposures at each dark exposure time.  The noise in the
DIFFERENCE of two otherwise identical exposures should increase as the
square root of the dark signal.  The same procedure must be followed to
get the photon noise from "flat" fields because for some exposure level
the pixel to pixel variations will be greater that the photon noise. 
Note that the expected noise in a difference is root 2 times the noise
in a single frame.

Fiaschi wrote:
> 
> 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
> 
> Marco Fiaschi
> - -- CCD-world -- --
> CCD-world is fully moderated. Send posts to CCD-world at astro.ku.dk
> Standard replies will go to the list; address personal replies manually.
> For more information, please go to:  http://www.not.iac.es/CCD-world/

-- 
Bruce Atwood
Director
Imaging Sciences Laboratory
Astronomy Department
The Ohio State University
174 W. 18th Ave.
Columbus, Ohio  43210-1106
(614) 292 6279 (V)
(614) 292 2928 (F)
- -- CCD-world -- --
CCD-world is fully moderated. Send posts to CCD-world at astro.ku.dk
Standard replies will go to the list; address personal replies manually.
For more information, please go to:  http://www.not.iac.es/CCD-world/