Let’s split things down a bit.

1. You have the algorithms - they take a set of data and work out where the optimal focus point is. The data could be a set of images plus focuser position or something like the current temperature and some preprocessed info for it to work out where the focus point is.

2. Backlash - this occurs afaik on change of direction of the focuser mechanism. Simplest solution appears to be to overshoot by some amount greater than the max backlash then move to the real position. It doesn’t really matter if the backlash varies each time or in either direction as long as the overshoot is greater. (I’ve no idea why NINA looks to have settings for both - this could just be the gui misleading me and only one is actually used).

3. Final move direction - in the case of sct’s with a focuser moving the mirror final the move direction needs to be against gravity. This move would also need to apply backlash compensation if it was a change of direction.

Current setup seems to not be quite right as it different parts seem to try and solve problems of other parts. I think the link between the backlash setting in the main gui needs splitting off from the focuser indi driver. Then the backlash compensation done independently of the algorithms and drivers if wanted by the user. The algorithms shouldn’t have anything to do with backlash. The indi driver could implement some focuser specific compensation if needed. The final move direction I think would be in the driver and would be active on every move that’s not in the ideal direction. This would shield the algorithms from bad positions without them having to know about it.

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