In my experience, typically the auto-focus function chooses an appropriate star to use as a focus target when "Auto Select Star" is selected (and this must be selected for an automated operation of the focuser). However, I found when shooting M8 that it consistently chooses nebulosity instead of a star, and this results in poor auto-focus results.
Refer to the attached screenshot.
Is there a workaround for this? I suppose other bright areas of nebulosity might be similarly affected.
Hy
Are you using subfield readout? The window unfortunately covers the respective radio box. I'd think the FOV is too small for the auto mechanism to reliably detect a star...
I'm sure sub frame and auto select start were checked, but don't understand why that would be an issue. The way it seems to work is it uses the entire frame to select the star the first time, or after reset is pushed, then it subframes on the selected star. The issue had to do with that first time, when it has access to the entire frame.
Was just something that jumped my eye. Probably mixed it up with phd2, that one for has issues when switching target in subframe mode. If it really first takes a full frame and then selects the nebulosity thats indeed unlucky
No real recommendation though. The full field focus mentioned by FENRIQUES seems to work quite nice in most cases within a target/sequence, but might need adjustment of the inner zone based on target.
I also sometimes have the issue that it is reporting the exact same value (1.00) for a broad range of focus settings, which makes the AF fail. I have not yet found out what might trigger this. In many/most cases it does work nicely.