Thanks guys. [Gals. Folks. Whatever. I may live in Madison but I'm old. I'm still learning this stuff the hard way: Having an ambiguously-gendered kid will do that for you!]

OK, now I think I understand what's going on with the algorithm; it's actually pretty much like what I thought it would be. And given that my backlash is something like 90 steps, and the linear algorithm moves out, then in, several times that at least every time it does a run, you'd think it would Just Work. Maybe there's another source of ugly of which I'm unaware.

I should definitely increase the tolerance, thanks for that suggestion. It's painful to watch it achieve really good focus, then move away from that to establish the other side of the curve, and then never manage to find that point again, poor thing! I think what I might need to do is bring a micrometer and actually measure where the focusing tube at these points on the curve. I tried to keep track of it on the fly by doing all the arithmetic in my head but that worked about as well as you'd expect for a tired old fart in the dark and cold.

If only I could work on this any time I wanted! I've even thought about poking a pinhole in a piece of cardboard, hanging that on the fence with a light behind it, and pointing the scope out the window at it. Who knows, it could work. Of course now it's not just cloudy but RAINING, so it would have to be something waterproof...

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