TheSkySearchers

I've been thinking about motorizing the dobson mount of my 12" tube, but I haven't come up with a mechanism to do that.
It looks like the stepper motors don't have much torque, and getting big enough gear ratio with pulleys is hard, because the size range of pulleys using the same size of belt seem too small.

How is it usually done?

You can get stepper motors with a gearbox built-in. I have a geared stepper motor driving my dome azimuth. The dome weights 180 lbs.

That's probably a quite big motor? 180 lbs is a weight of a grown man. :-)
NEMA17 sized steppers have torques around 100 oz.in.

Hey, thanks! You gave me the idea to search gearboxed steppers, not just steppers, and the search results are pretty different.
There are NEMA17 sized steppers with 100:1 ratio gearbox. They are not even expensive.
Looks like DIY motorizing is quite feasible after all. :-)