El Corazon wrote: In short, you need a stepper driven autofocuser with a strong motor, like a NEMA17. That should have no trouble pulling the weight of your light train when connected to the fine focus knob.

You can build one yourself, using for instance the MyFocuserPro instructions and the MoonLite Driver (as many others here have done as well) or you could buy a MoonLight focuser (expensive) or a Pegasus (some people I know have one and they are happy with it). Either way, I messed around for 2 years with analog focusers and since I put a stepper driven autofocuser together, all my stars are tack sharp in focus. No more bloated stars. Now I need to build one for my RC8 and for my ES102.