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Hello good people. I created a topic a couple days ago about flat frames and i uploaded some images when it was pointed out to me that my images have a bright circle in them and that it might be a problem within the imaging tube with reflections. I don’t know where to begin with this. I am using a skywatcher 150/750 pds Newtonian with a ts maxfield coma corrector (which I recently bought). I am just hoping that the coma corrector is not defective because it is giving me quite a lot of vignette as well to be honest. How do i go fixing this if it really is a problem? Can i work around this with flats? My flats seem to have the bright circle too. And just to be clear i am not talking about vignetting there seems to be a bright ring. here is an image to see what it looks like and i have marked the ring. thanks.  |
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| You have a light leak, either during the light exposures or during the acquisition of flats. Incidentally, it isn't the corrector that is vignetting it is the secondary that is undersized. |
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| Did you try longer exposures on your flats and bias? Multiple folks suggested this. I'm not sure why you needed to create an additional post for the same exact issue. |
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The bright circle is the good part, the black is the vignetting and the issue you need to resolve. I see a multi ring pattern in the bright area though, I don't know if that's just the way it looks here on the AB thread, but if it's still there when you stretch it and increase the black point then it's a tough issue to fix. And yes, your flats should remove the vignetting, I think. (my opinion) messierman3000 EDIT: If your flats are overexposed, then they wont remove the vignetting. This has happened to me; my flats were totally white (I used a white shirt with a flashlight FYI) and they visibly didn't help when I compared a flat calibrated light master with a non-flat-calibrated light master. |
