Peter, have a look at my recent post in the other thread on motor drives for the 16" dob.
http://www.iceinspace.com.au/forum/s...ad.php?t=26010
There is lot of infromation on the yahoo groups for eq platforms, that will help you make the electronics and guide you on the design parameters. There is a spreadsheet that will help with the calculations of various angles and radius's for the sectors.
Regards
Fahim