When I had aimed my TAL-2M - using the manual control knobs for precision aiming - I was very disappointed to see, that the object started to drift in RA almost immediately after I had released the controls. After say 10 seconds however, the object came to a standstill.
When visually observing this is not so bad, because you can gamble a little and position the object a bit 'upstream' and it will land more or less in the center of the eye piece. However, when imaging this is a biiig nuisance, because then you work in the blind. And gambling in the blind is a tricky business.
I found out that the play in my system was introduced by the gearbox/motor combination, and that I needed a motor corrector. I was astonished to discover that the thing I had bought to stabilize my 12Volt AC (yes, my TAL has 12V AC) proved to be a motor corrector!
What a motor corrector is and does you can read here!
I never touch the RA manual knobs, but by hand I push the OTA so that - when looking in the finder or eye piece - the object is right in the center.
To avoid damage it is of vital importance that the motor clutch is not too tight!
With my motor corrector I now have a lot of control over the RA movements: I can speed up/slow down using the variable speed control (a nice feature of the APM corrector!), I can stop and I can start, all without touching the telescope itself...When using my webcam I use the same procedure to centre the object in the heart of the preview screen.
On July 14, 2005 I started to use the motor corrector for Autoguiding !