I also use the Seletek controller (Armadillo2). In my case, a stepper motor from Robofocus is used.
What I wanted to know is whether the focuser of your refractor is Takahashi’s original rack & pinion focuser or whether the focuser was exchanged (e.g. for a Crayford focuser). This has nothing to do with the stepper motor.
As I wrote, R + P focusers always have some backlash. This has to be compensated, otherwise the Auto Focus will not work properly. SGP has a nice feature called “backlash compensation” for this purpose. In SGP, select Control Panel/Focus and select the button ‘Other’. Select ‘Focuser backlash compensation’, Compensation direction ‘IN’ and input the number of steps in the input field that is labeled ‘Compensation step size’.
The number of steps must be determined before. Move the focuser OUT by say 200 steps, read the focuser position and write it down. Then move it IN by a much smaller number of steps (say 20) and simultaneously observe whether the focuser actually moved. Continue to move the focuser IN by this small number of steps until you detect a movement of the focuser. Now read the focuser position again and subtract this value from the initial reading. That difference is your focuser backlash in steps. You should add some steps as a precaution, a too large value will not do damage, however, the value inputted in SGP as backlash compensation must not be too low.
I strongly advise you not to alter the ‘Advanced parameter’ of Seletek’s Configuration of the Focuser Program. If you experiment with these settings without knowing what you are doing, you possibly will damage the stepper motor. These settings have nothing to do with backlash compensation.
Bernd