[Issues] Crosstalk on CCD96 exceeds bias level

Ewout M. Helmich helmich at astro.rug.nl
Wed Apr 18 12:22:31 CEST 2012

Hi everyone,

We're investigating correcting the crosstalk of OmegaCAM. One issue that 
may require action on Paranal is that the crosstalk on CCD#96 (upto -600 
ADU from CCD#95) exceeds the bias level of ~400 ADU in CCD#96. See the 
attached plot. Pixels exceeding ~50000ADU in CCD#95 will put that pixel 
to 0 in CCD#96, destroying the information there (this in the absense of 
sky background, the background in the attached example is about 100 ADU, 
in g'). I see two ways to address this:

1) We can mask pixels with value 0 in CCD #96 (will have to for existing 
2) The bias level of CCD #96 can be increased by e.g. 300-600 ADU.

The question is if there are objections from a scientific point of view 
to this bias level increase.


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