I have now got my equipment setup as I want it, and am moving on to alignment mode.
I wish to use my C8 in both long 2000mm/f10 FL, and short 1200mm/f6.3 using a Field Reducer/Flattener, with my QHY8.
After going through a series of "what is the correct sensor to FR spacing" exercises, I think I have correct numbers now, thanks to IIS contributors and AgenaAstro.
I am putting the FR right at the scope visual back, followed by a Meade 1209 remote microfocuser, then the QHY8 with a 2" to T adaptor nose screwed into the existing camera T nose. The 2" section allows me to move the camera to trial various distances, as well as giving a firm mount. Spacing from the rear shoulder of the FR to the CCD sensor can easily be varied from about 78mm to well over 110.
Initial trials show lots of "space invaders" and eggies around the edges, basically pointing in a circular direction. Unprocessed pic attached. 10x2 minutes taken with PHD guiding on EQ6, which I suspect has excessive backlash, too.
My question: How much edge distortion should I expect at optimal spacing with a 6.3FR? I have both an Antares (220mm FL, spacing 81mm) and a Meade (FL=154/260mm, spacing to sensor: 57/105mm) according to the experts, post-2006 Meades are 154mm FL, but I'll try both settings. Both reducers were bought new this year from Agena.
I have done an initial star collimation on the C8, but I'm also not putting poor collimation out of the equation at this time. Still a lot of variables to take care of, that's why my question is: Just how good a picture at the edges should I be able to expect with a C8 and 6.3FR on a QHY8? I don't want to spend weeks trying to achieve the impossible, just the achievable
