(I'm getting 'Access Denied' replies on the idlers+mount.scad and picture, might be an escaping issue. ).This thing is for motorization of an Azimuth/Altitude mounted 300mm Dobsonian telescope.The idea is to have a belt running over large (>40cm) quarter circle pulley bolted to the scope and on a small (less than 1cm radius) pulley direct on a stepper motor. This should give zero-backlash, high-speed driving, with an accuracy of (assuming perfect 16 step microstepping) 11 arcseconds. With some more gearing down, better resolution is possible, but achieving zero backlash will be harder.Animation: http://youtu.be/Y1-zTE1iXZsUpdate: got the design returned from weight watchersTodo: printing, testing, resolution/accuracy tests.Longer term:Print the platePut skate bearings in the idlers, mount with (2) M6 bolts (hexagon holes on the underside)bolt to telescope (3mm holes preprinted) attach belt (6mm wide to match with the idlers attach your stepper and driver (intended for 16 microstepping with a 12-tooth T2.5 belt)follow stars with hand-crafted gcode?