I doubt you’ll need a lower geared motor Monte. You should have no problems getting the Robofocus to repeatedly hit within the FSQ Critical Focus Zone (CFZ) of 55 micron. Don’t tell me your still running @focus or @focus2. FocusMax all the way my friend, start being productive under the dark skies instead of troubleshooting your woes.
Just so we are on the same page. One pulse = one microstep. What you can configure is how many microsteps make a step. A step is what is counted by the Robofocus controller, so in another words what you are configuring is the number of microsteps per count.
The default step size is 4. So, the stepping motor goes through four microsteps before it completes one full electronic/magnetic cycle. One full cycle is small fraction of rotation of the output shaft. Typically a microstep is 0.0254mm (depends on the gearing used in the particular motor).
To explain: If the command to the Robofocus controller is for a movement (i.e move 42 steps IN), the controller begins sending pulses of current to the stepping motor. Each pulse will move the stepping motor one “microstep”. Meanwhile, the RFCP (software) has told the controller to consider that it will take some number (e.g., four) microsteps to make one step or count that the RFCP will consider. Thus, the RFCP command to move 42 steps will make the motor move 42x4=168 microsteps. The controller counts these steps, and after 168 microsteps will send the current position back to the RFCP for display. Note you can change the speed of the motor by changing the “pause/microstep” setting in the RFCP.
So the question is…what have you configured as your microsteps per step?
A 1:1 is rather extreme. Try it. If you can't hit the CFZ using this setting, something is seriously wrong! I’m currently running it as 3 (which is very fine adjustments) - provides ~4 steps (12 microsteps) in the CFZ (until I can see HFD and/or FWHM changes occuring). This may not seem like a lot of play, but with the repeatability of FocusMax HFD routine, it nails the CFZ everytime - even if through a Ha narrowband filter which shifts the focal plane (if not parfocal with your LRGB set).
