[Comm2011] FF - gain

[Ewout M. Helmich]

Yes I was wrong in stating the exposure level didn't change. I think I
looked at u' band images for CCD 65 for that. The CCDs in the corners of
the mosaic, in u' do not show much of a gain change, but in the centers
and for all CCDs in the z' filter the change is clear.

Ewout



On 04/14/2011 09:22 AM, Konrad Kuijken wrote:
>
>>
>>
>> - when comparing similar exposures with different electronic filter
>> settings in fact 31 out of 32 chips show signal changes corresponding to
>> gain change deduced from the "gain recipe". So it seems gain recipe
>> works well, and there is indeed a different effective gain for different
>> filter settings.
>>
>
>
> Hi Edwin,
> THe fact that the gain recipe gives different results for different 
> filter settings does NOT necessarily mean the gain changed. The recipe 
> assumed that the filter does not have any smoothing effect but this 
> may be wrong. So photometric tests of the gain are very important.
> Can we do this test quickly?
> Koen
>
>
>
>
>
>> All this will be further investigated coming days.
>>
>> its amazing we can already do all those things!!
>>
>> When involving astrometry, which we can , we can even have a look at
>> gain changes over the fov and  and make fisrt guess of illumination
>> correction. Will be done coming days.
>>
>> Edwin
>>
>> -- 
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