I took a few 4 minute subs of the horsehead nebula with my 12 LX600 (F/8) and the ZWO 071MC Pro. I also had the attached there 0.62 Lepus telecompressor (F/5) with the Antlia ALP-T HA & OIII dual band filter. I never got passed the first few images because of a large obstruction that looked like a faint defocused star cover most of the FOV.
I was at the unity gain of 90. Could it a reflection of the closely star, Alnitak or maybe a reflection of my secondary? I'm just guessing at the problem. Lastly, could it be a problem with the camera. I did have it cooled down to -20C before imaging. Any help to this problem would be appreciated. BTW, I have imaged other deep sky objects without this problem.
Thanks very much
Art
