ChrisRowland wrote: This is a common way of implementing backlash. All moves approach the final position from the same direction and distance. This eliminates backlash by ensuring that all moves finish in the same direction. Backlash is your M parameter.
The example shown seems to have found the minimum with the focuser moving out instead of in but there is nothing except friction stopping the camera moving out the 100 steps of the backlash and being out of focus by 100 steps. If the focuser finishes by pushing the camera in which, with the telescope looking at the sky, will be up there will be less chance of unepected focus shifts.
hy wrote: Pit: join in!