[KIDS] Crosstalk on CCD96 exceeds bias level

[Massimo Dall'Ora]

Hi Ewout,

interesting plot....

>From the stellar photometry point of view (that is my point of view), to 
increase the bias level has no scientific effects, apart of to slightly reduce 
the dynamical range, and to increase the noise of the measurements at high 
magnitudes.

Probably some issue could arise for the extended sources, since an increase of 
the bias level of ~600 counts introduces an additional noise of  ~25 counts, 
that could mask faint features.

Regards
massimo

On Wednesday 18 April 2012 12:22:30 Ewout M. Helmich wrote:
> 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
> data).
> 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.
> 
> Regards,
> Ewout