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On my LX200 I use a JMI NGF-C which is permanently equipped with a RoboFocus unit. Unbeatable. Using FocusMax focusing is a 1 button exercise, taking usually about 45 - 70 seconds on a Mag 7 star. It's easily scripted in to automation each night.
The RoboFocus has been having a few heat issues lately, not sure what's going on. It's been working solidly since about 2003.
On my Megrez I have an Orion Acufocus. It's sufficiently "fine resolution" to accurately focus easily, but doesn't have the PC interface of the RoboFocus so lacks the auto-focus capability. For the money it's great, but if money is irrelevant I have no doubt I would get the RoboFocus instead.
The RoboFocus has absolutely no backlash or slop. It's accurate to an extremely high level, really I can't fault it at all except for the recent issues with heat which I expect are due to such constant usage for 5+ years.
Back when I bought my RoboFocus I chose it over the JMI equivalent because it was reported to be of higher procision due to it's usage of stepper motors and temperature compensation. Certainly it is useful being able to exactly position the focuser at position 186 if you know that's exactly where it should be (range for my JMI is about 5000 positions from fully in to fully out).
Roger.
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