I was hoping they’d mention a Bahtinov mask - it works on the same principle, and is very common even in amateur astrophotography. The Wikipedia article for it

I was hoping they’d mention a Bahtinov mask - it works on the same principle, and is very common even in amateur astrophotography. The Wikipedia article for it has a more in-depth version of how it focuses itself. https://en.wikipedia.org/wiki/Bahtinov_mask https://en.wikipedia.org/wiki/Bahtinov_mask