Method for limiting largest star size

Lately I’m having some issues with large stars in a frame (with diffraction spikes on a Newton) where the auto focus routine will latch on to the large stars cause inconsistent and poor focusing. Since there are plenty of smaller star in the frame, would it be possible to limit the largest star size to be considered for auto focus? Or maybe some form of clipping on the data for robustness?

Adjusting the “Minimum Star Size” for autofocus also adjusts the “Maximum Star Size” (somewhat counter-intuitively).

(Or, at least, that was true in 2.x, I presume it still is in 3.x)

That doesn’t seem to be documented at all, would lowering the min size also lower the max size? What is the relation there? Personally I’d prefer being able to change these independently or better yet, allow something like percentile clipping

That doesn’t seem to be documented at all

It is, but not easily findable. You’ll see reference to it in occasional forum posts or release notes. For example, the 2.5.1.8 release notes includes :

  • Increased the maximum star size (still a function of minimum star size). Both sizes are logged if you want to see them.

What is the relation there?

As best I remember, linear…that is, reducing minimum by 1 reduces maximum by 1 as well, but don’t quote me on that.

I’d prefer being able to change these independently

Agreed.