The high resolution encoders that will help Dec and correct backlash can not be interpolated encoders - they won't work to see and correct backlash. Interpolating encoders only work on RA because it is constantly moving, tracking at a nearly constant rate that allows interpolation to work. A 1 million tick encoder has 1.3 arc-sec resolution, so it would never get closer than the last 1.3 arc-sec. Only the Servo II can operate with mount encoders of this number tick/rev and higher - the Servo I can't read that many tics.
