Since f/ratio is known, "Critical focus zone in micron" could be calculated automatically (also with ccd-corrected formulae since we know sensor pixel size too). So only needed parameters are "Microns per motor step" and "Step size (CFZ units)". For "microns per motor step", I think the best approach for non technical users is to provide them with two fields: "maximum focuser travel (mm)" and "maximum steps (for total focuser trave)" and let the code do the division. This suggests the users to measure the max travel and not, to say, the needed steps to travel 1 cm, which is useful to reduce impact of inevitable measure error.

My 10 cents.
Matteo

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