I have an Atik 383L CCD. If I do Darks in the Atik softwarArtemis, I can set it so that the mechabical shutter does not open during the exposure. I would prefer to do Darks in SGP. If I set a sequence for Darks, does SGP ‘instruct’ the camera to keep the shutter closed during a Dark exposure. I ask because I did some Darks in Artemis and these were fine. I then tried Darks in SGP and found a bright area to the left of the resulting image. I have included a link to a 30 minute Dark captured in Artemis and an 8 second Dark (intended for use as a Flat Dark) in SGP. Ihope this demonstrates the issue.
The short answer is that SGP should keep the shutter closed, IIRC (I
used to use a 383L+). It’s not unusual to see a bit of glow along the
sides with this camera, but your 8sec dark is pretty extreme. I would
first take some 30min darks with SGP and see how those compare to those
captured in Artemis.
Just got back from the observatory. 8 second darks with Artemis showed no abnormalities. I then went back into SGP and tried some 8 second darks there. Lo and behold they were entirely normal too. I’m not sure what was going on the other day, therefore. I had been experimenting with a new luminance panle for flats just prior to doing teh darks and I was having a lot of trouble dimming the panel sufficiently. The flats kept blowing out. I don’t know if that was the cause - if so it affected all 25 of the darks I took.
In any event, today the SGP darks looked identical to the Artemis ones.
Try capping your scope. The shutters aren’t perfect and you often can get some light in that is unexpected. I try to shoot my darks at night (stray light gets into observatories during the day) and can wreck them.