hy wrote: Sorry for that delay. I will get back to it at some point (the linear focus algorithm--yes, scanning through in one direction then reversing to find the best point) .
WRT backlash, I did look to see if it was trivial to find (and eliminate) the backlash in my Moonlight focuser, and I will say
(a) it's clear I have backlash, and
(b) the number doesn't just pop out in the V-curve when you go back and forth--there's other noise in the system that hides it a bit.