Auto focus step calculation

I have used the exact formula you supplied many times for calculating the auto focus step size and just cannot seem to get the results you do.https://mainsequencesoftware.com/Content/SGPHelp/lib/NewItem556.png

Ive followed the instructions exactly as you have out lined them and received different numbers. The other night my step size, per the calculation was 150. That worked for a short time, then I was having issues. I redid the routine and came with 16, that was a disaster. So, for no logical reason, I simply set the step size at 75 and it worked before I hit the hay this morning. What is the trick here? In your instructions the example doesn’t provide a current in focus number, so its difficult to check even you math. Im no mathematician. SO what is a good round number to use? I have a Televue 127is, a feather touch Focus Boss stepper motor with about 19k steps per inch…thanks

You’ll need to find good focus first using a bhatinov mask or other methods. You can use the HFR readout in SGP and manually move the focuser until you get a min HFR. It doesn’t need to be perfect…but needs to be close.

Thank you,
Jared