Hi Ron,

What do you mean by "only get good focus about half the time"? What happens in the "bad half"?
Sometimes (nowhere near half) I get an especially low HFR value, or even a seeing change so the whole 2nd pass has higher values, and the algorithm often does not deal with that very gracefully.

I also pre-focus at the start of the night. I use the manual single-frame capture button and check the reported HFR. I have a pretty good idea what is right for in focus. If it is higher, then I manually step the focus motor and check again, repeating as necessary. One tip I just learned from this thread is for times when I have changed the setup more drastically I might uncheck full field for the early part of getting to nearly focused, just to speed up the calculation time.

I, too, had wondered about the fact that the stars being evaluated change as focus changes, but Peter's explanation makes sense.

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