Am I using my flatter correctly?

[E_ri_k (Erik)]

Hey guys, I have a WO Flattener 4 which I am trying to use with my Vixen ED80.

My method for finding the correct spacing was to centre on a large open cluster, with some good stars in the corner of the image, and adjust the flattener, refocus until the best possible result was obtained.

No matter where I position it, I don't notice a difference on shape? Is my procedure wrong, or perhaps the flattener is not compatible with the scope
Erik

[White Rabbit]

I have the same flattener and there is no way I'd be able to get the correct spacing with out CCD inspector. It shows you the curvature and takes the guess work out of it. I think they offer a trial version.

Sandy