David Bennett replied to the topic 'Auto Focus failures' in the forum. 2 months ago

Hi John. ... a further question, how does auto focussing handle backlash? The one pass linear algorithm winds the focuser in one direction when capturing images so no reverse in direction and backlash doesn't come into play, so at the start moving out to initial start position and when winding back to computed focus position is when backlash is important.

The ASI EAF manual describes how to estimate the backlash and this gets saved to the EAF. The Indi driver confirms this as it has the setting I set up using the ASI software on my laptop.

Now there is a backlash value on the mechanics tab and first time it is the same as the indi driver. If I change it here I believe it changes it on the Indi tab which updates the value saved on the EAF. Is this correct please?

Now my knowledge gets muddy. If the EAF is commanded to move to a set position which requires a reverse in direction it will internally adjust for backlash. This means the step count doesn't need to be adjusted by the auto focuser otherwise this will double handle the backlash. However examining the log file auto focussing routine does adjust count for backlash.

If I have got this right (probably haven't) I dont think auto focus should compensate for backlash with a ZWO EAF and I wonder why the backlash is even there on the mechanics tab.

Could you clarify what I have got wrong.

Thanks
David

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