[programmer]

Well everything went well with the mounting of the encoders. Trouble is, during initial setup, I'm getting 'alt encoder error'. I start from vertical, and slowly move the scope down in Alt. At about 36deg from vertical, the deg/min/sec readout starts to falter, then I get the above error. It seems to start up again as I get close to horizontal. If I just take the alt encoder off the scope and twiddle the thing by hand, it's happy. Obviously it has issues with the mount, but I'm not sure what it's unhappy about. Anyone have similar problems initially? Edit: ok seems to be the problem solved by the 'fencing in' of the encoder, in your first link Eric. Re-reading that now...

I do still have some side-to-side play, but I can't really see how that would cause the above.

PS: Changed the name of the thread to be more generic