I wonder if anyone can help diagnose the source of the odd bright arcs visible at the top of the attached image?
It was taken with a GSO RC10CF and SGBIG ST2000xm. There was an AP CCDT67 FR in line and a FW fitted with Astronmik filters. I used DSS to calibrate and stack the images.
It does not look like reflections in the FR to me.
Could it be a result of field rotation (my polar alignemnt was not accurate) and processing (I did not do use flats but did use darks)? I do not see these issues in the subs even when pushed hard...
It's not field rotation. I've never seen anything like it. There are two sets of concentric rings centred top left. It would seem that the fainter one might be a ghost of the 1st. Do you have any light that could be shining back into the scope from a bulleye somewhere?
Did a bit more investigation the arcs appear in the Ha and Sii stacks but not in the Oiii. The fainter arcs are from the Ha. Very odd. I think it must be a processing anomoly.
i think this maybe from stacking frames that have too much movement between exposures. i have this image from may 09 that was stacked in dss. i cant remember how many frames were taken, but i used a point and shoot that took an image at 5 second intervals. no dark or bias frames and obviously it does not appear in the individual frames. my 2 cents
Sebastion - thanks - that nailed it. Not sure what I did wrong on first pass but re-stacking has made the issue go away...interesting shot there - it looks a bit like the lighthouse buildings on Montague island....and never thought of trying handheld AP - very creative!