Looks like I was misunderstanding NINA.

The relevant page is nighttime-imaging.eu/docs/master/site/advanced/autofocus/

They have two types of compensation.

1.Absolute where it adds on a set of steps at a change of direction - looks to require knowing quite accurately your backlash. Not sure if this can have different numbers of steps for in and out as it doesn’t say but the gui having both seems to point to a possibility.

2. Overshoot which moves past the point then back to it. This has either in or out steps set but only one. This is so the focuser always completes its movement in one direction.


There’s a tip later in the manual - “ Overshoot can be very useful for SCT users to avoid mirror flop. In fact, when setting the Backlash Compensation to IN, the last focuser movement will always be outwards.”. Looks like NINA uses this rather than a switch like I was suggesting. I suppose the extra back and forthing is of little consequence just doesn’t seem tidy to me.

Now time for me to check whether the Celestron sct does the backlash compensation wiggle each move or not..

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