QHY8L and coma corrector

[Stu Wilson]

hi guys.

I seriously need to add coma corrector into my train.

Running imaging camera QHY8L I think I need the skywatcher coma corrector/ .9 reducer.

However I read it needs 55mm back focus.

Can someone please tell me. Do I screw the cc onto my camera and it needs another 55mm than normal further out of drawtube or do I need 55mm between my camera and cc?

Very confused but need the answer before I venture down another costly path.

Cheers guys for replies.

 

Stu 

[fozzybear]

take a look at his old thread and hope it helps you out.  You would need 55mm from the CC to the camera that is attached

[almcl]

The distance between the flange on the Skywatcher Coma Corrector and the sensor needs to be 55 mm (your second statement).

But, I have used the SW CC for some years now and while it flattens the field on my 200p, it suffers serious reflections if there's a bright star in or near the frame.  I recently upgraded to the Explore Scientific CC, which although longer and heavier (and more expensive), does a much better job of suppressing unwanted reflection artefacts.  The Skywatcher version reduces your effective focal length to 909 mm (according to calculations from All Sky Plate Solver) while the ES one increases F/L to 1065 mm.  Not really significant but of mild interest.

Edited August 11, 2020 by almcl