I have been using a NGF-CM for my Ranger for quite a long time. Like some amateur astronomers suggest, motorized focusing is somehow a must for imaging since whenever you touch the focuser, you will affect the image and so hand free focusing is a good way to get into a better focus.
NGF-CM brings too benefits, one is motorized focusing and the other one is 2" capability. I really love my Pentax XL 40mm but then it's probably the only reason for me to keep the NGF-CM.
Today, I pulled out my original Ranger focuser and I believe that it might not hard to motorize it, and I might even use the small DC motor which I've used to motorize the 127mm Maksutov! I just need a longer belt.
I shall explore that a bit further, it saves some more money by kicking the NGF-CM out of the equation. Actually, the NGF-CM has a third benefit but it's no longer applicable to me, it's the capability to allow the use of a stronger reducer for taking H-alpha full disc image in one shot.
A 45-50mm belt should work for my Ranger, however, problem is, the helical focuser will move along with the draw-tube, so the motor fixing mechanism has to be movable as well.
A 35-40mm belt should work for my 127mm Maksutov.