Please help – first light disaster

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Detlef Scholz avatar
This is the result of the First Light session with my new RC12 https://www.astrobin.com/r1jjrs/
On the Original you see the picture without flats applied
Rev. B is the same picture with flats applied
Rev. C Is the master flat and its curve to create the flats I use a flat panel. I use this for a long time without problems with my APO’s(monochrome and OSC) 

The Flat is created from 15 subs with about ADU 32.000. For the Subs I used the APT Flat tool but tried also a few different exposure times without any noticeable change. The RC is a from TS Modified RC “astrograph” TSRC12T64 with a 0.8 reducer, suitable for full size sensors. Since this is my first experience with RC Telescopes I don’t know if the Vignetting in the first place is OK / normal. I expected this to be corrected by the Flats but the vignetting on the flats seems to be less than those on the lights. 
Does any of you has a solution to this Problem or knows what could be the cause?
andrea tasselli avatar
Did you subtract the master bias/bias-dark from the flat? And what about the light frames?

Here is what a OSC flat should look like:

Detlef Scholz avatar
Thanks Andrea, yes i use WBP to create the Master Flat Bias and Darks . in the Moment i follow @Adam Block's Video pointed out by @Almos Balasi. On the other hand Your Histogram looks better then mine so the problem also might be caused by the Flatpanel. Lots of hings to try out …
andrea tasselli avatar
Can you do that manually instead? The hystogram of yours shows a peak were there should be none.
Detlef Scholz avatar
Thanks Andrea. You are right, i have to check my flat panel more deeply. But for the moment my problem is solved . The cause for the over correcting where to old dark's that did not match the flats / Lights.
Mohammad Nouroozi avatar
You need to shoot dark flats. while bias noises are variable in CMOS sensors and depend on exposure time when you are using dark frames it automaticly subtract bias noises from your lights and also dark flats will subtract biases from flat frames.So you should not take bias frames . this is the Key! in this case bias frame will add flat fielding problems to your image.
Detlef Scholz avatar
Thanks Mohammad, i actually took also some dark flat's. Maybe this also helped.