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I have a Celestron motor on my C925 and it seems to be repeatable position wise. In SGP you need to reverse the focuser direction and then use backlash compensation on what becomes the "Out" direction (Down the baffle) and use around 1000 steps (A full turn of the knob) of backlash compensation.
You have to reverse the direction in SGP as Celestron don't provide that functionality in the driver and they regard "out" as being away from the rear cell, which focal plane wise is equivalent to "IN" on just about every other telescope design. If you don't reverse them the focus routine in SGP will step it "Out" (Up the tube) and then every focuser move during the focus run will be "IN" toward the rear cell and have backlash compensation applied. It all amounts to extra focuser wear and extra time taken on every single focus run, of which there will need to be plenty to keep the temperature related drift under control.
Downside at least to the first series Celestron motor is they do not have a temperature sensor built in which I think is a bit of a dumb idea for such temperature sensitive scopes. In the summer I was trading extra subs for sharp subs and having it do a focus run about every 15 minutes as early in the night it could go from pin sharp to doughnuts in that time. If I was going again I would probably adapt a ZWO EAF on to it to have the temp sensor.
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