@Bart: Re: "would you consider to focus during imaging or quickly adjust the focus in between lights?"

Well, the data for my fast (f/2.2 setup) indicate that I "could" change the focus by 60 counts per degree F change, and ~21 counts per degree elevation change. It's tempting to think about an experiment with this and do a build where an auto update is done between exposures. I also do short (30-40 second) subs, so an autoupdate might keep me from having to do an autofocus run (expensive!) so often at the start of the night. Whether I'd trust it for a big elevation difference slew is another topic, but it would be an interesting test. Eventually, and assuming a stable focuser with well controlled backlash, it might be quite effective at reducing the need for autofocus runs.

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