I bought this toy for around $450 when I had dreams of computerising my 8" dob. It seems to work ok but I have never got around to fully setting it up.

There are two encoders. One sits on the base for the azimuth readings. The other sits on the altitude axis. Then both encoders are connected to a handheld controller for display the RA/DEC, ALT/AZ or to search for an object. A serial connection for a PC is also on the encoder. I had some success in connecting this up to the Skymap Pro commercial software for displaying the telescopes position on detailed star charts.