Hi,
Earlier I have made a calculator to find the telescopes depth of focus:
http://www.astrofriend.eu/astronomy/...-of-focus.html
Now I have continued with a gear ratio calculator for the motor focuser:
http://www.astrofriend.eu/astronomy/...box-ratio.html
Sometimes it could be tricky to find the correct gear ratio and maybe this could be of some help.
It's important to have the stepsize about 5 times smaller or even less then the depth of focus.
Note:
This is all new, I may have done some mistakes, check carefully before ordering any parts!
/Lars