I know this is an old topic but rather than create a new one for the same item, I would like to add to this one and also recommend adding the backlash compensation option.
While I believe the gravity argument above does have merit, it depends on how smooth the action is on the focuser whether the weight of the cameras (And the angle of the equipment) will pull the focus to it’s outward most point at rest. Not everyone is able to image at or near zenith.
As another hobby, I retrofit manual machines that perform metal work. CNC Mills, Lathes, Plasma tables, etc. They use rotating ball screws that drive heavy tables to move material and no matter how precision you purchase in this hardware, there will be backlash present to some extent. If no backlash compensation is applied in the machining control software based on the measurements of the machine movements, any parts that are created will be undersized because the equipment did not move to the expected location to perform the work. When you are working with dimensions in the .001" range and less, that makes a big difference in a scrapped part or not. The same would be true here in the focusing side.
I use a Rigel System Nstep, I know from using a dial test indicator exactly how many steps my focuser must move to be accurate both in and out but there is no where to enter this into the software for compensation to occur. From my perspective, It doesn’t matter whether moving in or out on the focuser. If adjustments are made and the focuser has backlash steps that aren’t cleared out and compensation applied, then a repeatable location does not exist when running the routine. Due to this, my focus runs always end up with a sharp hook on the right side because of the backlash introduced by the focuser. That said, these are on the factory Explore Scientific focusers on a refractor I use for AP, but it wouldn’t matter if it was Moonlite or Feathertouch, etc. Backlash is backlash and if it can’t be trained out of the system, then the slop introduces errors in the motion and calibration.
Having this setting would allow the system to account for that and not undershoot/overshoot target settings and make focusing less of a hassle. In Mach 3 (The software I use for my machine work) there is a wizard that allows you to easily determine the backlash and something like this would make setup easier for the user getting started. I don’t use the wizard any longer because I use screw mapping to determine wear in a similar way PEC works but initially on my machine. It would help to have a general backlash compensation in the system for users that need it. Starting with just adding that would be a blessing and the wizard later maybe…