slow rpm dc motor

The speed of the DC Motor may not be as important as the speed of gearbox output. Typically the motor run at thousands of revs per minute and the gearbox steps this speed down and torque up to something useful for your application.

regards, colin

It also depends on how quickly you want to turn the dish, the mass and orientation of the dish ect. There are some motor and gearbox combinations that are useful for small projects Also i believe you can often purchase dedicated satellite tracking systems or motorised mounts that are probably cheaper than you could make them

I hope that can help a little if not can you give us more information on what you need?

You might want to look into motorized telescope mounts. Some have geared bases that track night sky objects for timed exposer photography. The sun is a star right?

If you want to track the sun, build a sun tracker. Edmund Scientific has a little one here:

All you need are two solar cells arranged in a wedge as shown. Use comparators to drive relays to run the motor in one direction or the other.

You can build this out of op amps and relays, or use a microprocessor. I'd be inclined to use op amps, because you can power the tracker off the solar panel without worrying too much about what happens during low power conditions. After all, when it's dark, it doesn't matter where the collector is pointed. Allow for a dead band, so when the outputs from both halves of the wedge are nearly equal, the motor doesn't run.

The Art of Electronics by Horowitz and Hill covers op amps and comparators quite well.

Read this manual for a commercial solar panel tracker:

John Nagle