Trull

Its hard to count teeth, I suggest using a sharpie marker to tick every tenth. Works for me anyway.

I polar align the GP-DX using the inbuilt scope, its accurate enough and is very quick to complete. Particularly if I use a compass to find north.

I'm happy taking 2 minute subs, at ISO1600. Have not noticed any improvement on mirror lockup, so don't bother anymore. Always remember to take darks - about 80 is plenty, and bias frame, although no light frame. Try to capture about 100-120 sub frames which is long enough!

...needless to say I bought the stepper control chip. Not that that helped with my drive mechanism, but at least I can stall my stepper with the best of them!