AmpedInventor
29-12-2021, 10:20 PM
Hey everyone!
I have a SkyWatcher ED72 and it's associated 0.85x reducer/field flattener, and I've been having issues with severe star astigmatism in one corner of the field (and, to a lesser extent, the directly adjacent long corner)
Rotating the camera and field flattener with the field rotator 180deg causes the astigmatism to rotate 180 degrees. (Note that the telescope stays in place)
My 1600MM Pro should be at the right backfocal distance of 56mm. (including the +1mm distance for the mono filters)
The most likely problem that may attribute to this problem is a broken rubber O-ring in the front element of the flattener/reducer. It has snapped, and so the glass elements inside are free to move about without it inserted. I have pressed the O-ring back in as far as I can. It successfully secures the elements in place, however I suspect they may not be perfectly aligned. If requested I will post photos of the flattener.
I have attached the aberration inspect window from NINA and CCDinspector images of before and after a 180deg rotation.
I'm happy to provide further information if needed.
I'm mainly looking for solutions to the issue or further ways of diagnosing the issue. Any advice? Could a tilted flattener element be the issue?
I have a SkyWatcher ED72 and it's associated 0.85x reducer/field flattener, and I've been having issues with severe star astigmatism in one corner of the field (and, to a lesser extent, the directly adjacent long corner)
Rotating the camera and field flattener with the field rotator 180deg causes the astigmatism to rotate 180 degrees. (Note that the telescope stays in place)
My 1600MM Pro should be at the right backfocal distance of 56mm. (including the +1mm distance for the mono filters)
The most likely problem that may attribute to this problem is a broken rubber O-ring in the front element of the flattener/reducer. It has snapped, and so the glass elements inside are free to move about without it inserted. I have pressed the O-ring back in as far as I can. It successfully secures the elements in place, however I suspect they may not be perfectly aligned. If requested I will post photos of the flattener.
I have attached the aberration inspect window from NINA and CCDinspector images of before and after a 180deg rotation.
I'm happy to provide further information if needed.
I'm mainly looking for solutions to the issue or further ways of diagnosing the issue. Any advice? Could a tilted flattener element be the issue?