Andrew, You could make a Dave Ek encoder box which plugs into your serial port. It works fantastically well for my two scopes,I've done it for my 8" and 12":
http://picasaweb.google.com/dudley.geoff/12InchF6DobsonianTelescope I don't know if Dave's box will work with mouse encoders but you could email him, he's very approachable. Here's his website: http://digicircles.eksfiles.net/ Good luck! --geoff
