[Comm2011] FF - gain

[Edwin A. Valentyn]

A few interesting notions of the day:

- applying dome flats to sky data shows <5% center to edge large scale 
variations from center to corner mosaic, so dome screen seems to deliver 
pretty homogeneous illumination

- however twilightflats  give better results than dome flats on sky 
data, most likely because of presence of structures at all scales i.e. 
pixel, 100 pix on  chip, and >> 100 pix screen.

- 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.

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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Prof. Dr. Edwin A. Valentijn       University of Groningen
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