Hi everyone and Hi Doug ! My CCD is STXL 1102 I have a problem with these frames and i dont' know what cause it. Each frame is 600 second long in Bin1 at -30 I noticed that in the lower left corner there is a very obvious artifact and I don't know what it is due to. It is certainly not a nebular signal (or yes) ! It is present in all three frames R G B but in the relative flat field is not present !!! Can it be a frosting effect or what ???
So you exclude that it is a frosting problem ? Could it be caused by the light emitted by a Power Supply display at the base of the mount?
It does not look like frost to me. That said frost can take on a lot of bizarre appearances. This will not be an external light source. It would be a bright star just outside the field reflecting off some internal surface in the optical train.
That is pretty far off-axis, so if it is a reflection it would have to be something well in front of the camera. It could be something bright but not-that-bright that is closer to your frame. Look for something right on the edge. Next time you are at the telescope try imaging the field again. If you see a reflection try moving the telescope slightly.
