Thanks so much everyone.
The Sampson Mount uses a 50 Hz synchronous motor that drives the RA axis at around sidereal rate. It runs through a drive corrector with a hand control with Fast and Slow buttons that either speed the motor to about 70 Hz or slow to 30 Hz on a hand control. There's also a fine speed control knob on the hand control.
The guide star is highly magnified. See pic. Each square is a pixel and at 1400mm fl would be about an arc sec maybe less.
As soon as I see the star drifting in RA I use the fast or slow buttons to keep it centred. Drift in DEC is very slow and doesn't need much correction by means of old fashioned slow motion hand control because Sharpcap gets me so well polar aligned. See next pic.
The Sampson drive is quite predictable in its periodic error. Each time the worm takes up another tooth it will speed up and slow down or vice versa. I use the fine speed control knob to match this as best I can then make quick presses on fast or slow buttons to keep that guide star right on that reticle.
Yes the drawback is i cannot leave while the scope is imaging. I have to be there watching the screen to make those constant corrections. But I can have music on, or have TV in a window on the laptop. On a weekend it's often the footy! On one Friday night I even participated in a zoom meeting with our Newcastle astronomical society while I imaged! Multitasking at its finest haha
Its rare i have to throw out a sub unless its a bit windy. I always balance the scope slightly east heavy so its constantly meshing against the worm wheel to avoid backlash. All 11 subs in last night's session were kept.
Its fun extracting what I can get out of this ancient system. I still think I have it easier than the bad old days of hypersensitised film and single exposures that had to run an hour or more, and not know it worked till it was developed
