OAG on my EdgeHD

[boz_m]

Quite a specific question here. I capitulated and bought an off axis guider (OAG) for my 8” EdgeHD as I had troubles with differential flexure with my guide scope. I am aware however that the EdgeHD has specific backfocus requirements of 105mm when using the 0.7x reducer. I had all the right extension bits to get this but the OAG adds 16mm.

How hard and fast is the 105mm requirement? What effect will I get if I go outside this?

If a problem I will have to look for a spacer that is the correct length which will be tough. Cheers

[Marke]

Depends on the size of your camera sensor the spacing is just to give the flattest field over the largest fov .The 16mmm over on a chip that's less than a full frame sensor may not even be noticeable your centre will still be sharp . So basically the further your spacing is off the faster the flat field will fall off. So dont sweat it and just try it and see what your field looks like first.

[Chapstick]

I believe I read in either the edgehd whitepaper on in the documention for the celestron OAG that within a few mm is recommended. You should be able to get an adjustable spacer worst case.