A harmonic drive is a speed reducer with high ratios with very high efficiency and no backlash. At very high ratios they are non-reversing too. Harmonic Drive AG offers them in a package with bearings and sealed housing, load and torque ratings that far exceed the needs of a telescope mount. To increase the reduction (160, but in fact 161) I added a planetary gear that slides inside the hollow input shaft of the harmonic drive. This drive on the Mountegra will serve you for eternity.