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Weird flats
Just testing a new camera (ZWO ASI1600MM-C) on my GSO RC8 scope. I am getting flats like the attached.
This is heavily stretched, and the differences are quite small, i.e. 27000 ADU in the centre and 29000 at the edge. The shadow at the top is from the OAG and is about 24000 ADU. But my question is why is it darker in the middle rather than lighter than the edge?!
Setup is an ASI1600MM-C + filter wheel (1.25" Luminance filter) + OAG + CCDT67 reducer.
Not tried it on stars yet as of course a week of rain has greeted my purchase!
Anyone who can advise if there's an issue or what might cause this centre darkening please?? There's nothing there in the bias frames so seems to be a property of the optics and not the camera. But my previous setup with a QHY8 and AstroTech flattener showed a brighter image centre as expected.
Thanks,
Paul
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