Quick Q on f/3.3 and filterwheel

[jmelquist]

Need some quick advice. I have a C8 (f10) scope, a filter wheel, a Meade f/3.3 reducer, and a ATIK 320E (small sensor). I'm trying to get a combo which has no coma and gives me as large an FOV as possible. I hear that spacing is crucial to eliminating coma - down to the millimeter. But the reducer comes with 15mm and 30mm spacers and the instructions say to get f/5 use the 15mm and to get f/3.3 use the 30mm spacer! so what gives? are there 2 points where coma is eliminated? How do i go about experimenting w/o buying every T-thread spacer in existence? it's not like i can hold the camera by hand to try out all the different spacings...

I guess there are 2 spacings to consider: 1) between scope and reducer and 2) between reducer and camera. I'd like to get my filter wheel against the scope directly as I use that for my lunar/planetary imaging as well and don't want to reconfigure my entire imaging train to switch between FR/ATIK and FlipMirror/DMK.

if anyone has any experience with this setup or with how to efficiently experiment on spacing, i'm all ears.