Hi Kurt,

I've only ever attached my stepper motor to the fine focus shaft, never the course focus, so I don't have any direct experience. But I know some people use stepper motors with built-in reduction gearing, and attach to the course focus shaft. The gearing will add some backlash, but at least some of the autofocus algorithms (linear, for example) compensate for backlash by always approaching focus from one direction. So I would recommend using linear algorithm with a geared stepper.

-- Kevin

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