Firstly - Ben, a fine image, and one that interests me greatly. I have a similar setup (FLT91, ZWO 2600MC Duo, and the
flattener not the reducer) and despite schematics, e-mails to WO, and some liberally applied invective

I can't quite get the backfocus right, so I congratulate you on what you've achieved.
Martin - interested in what you did there. Gain 0, huh? (Wanders off to make further adjustments...

)