Using Asto-Tec AT2FF with TV-85 and Atik383 OSC

[jsbianco]

I have been trying to use the AT2FF field flattener with my Telvue 85 and Atik383 OSC and still cannot get the backfocus correct.  The AT2FF asks for 57mm +/- 4mm and using the 17mm to the ccd chip I am using 60mm backfocus and still have stars at the edge that are out of focus.

Has anyone else used the AT2FF with a TV-85 and Atik383 and found the best backfocus distance?  I will be doing another test using 61mm to see if the field flattening improves.

Joseph