Very interesting. It's always fascinating and strange to see light behave as a wave since even though we know it does, it's not always readily visible in everyday life.
Do you use homemade Bahtinov masks when you observe, and if not have you noticed a major difference between purchased and DIY ones? I'm wondering if there would be any difference in operation since it seems to just be a specially made array of slits.
I've only ever used homemade ones, but most of the time if I want really good focus I will use the FWHM method on a star. But the Baht masks are revelation if you've only ever done by eye focusing - just line up the crosshairs!
It's very interesting that you use FWHM - I've seen that exact concept come up a lot in several physics courses, but always about oscillations or electrical filters (Q-factor basically). Funny how stuff like that comes up in seemingly disparate fields. But minimizing the FWHM for a telescope would be analogous to increasing the Q-factor for a RC filter, which is optimal and gets a "sharper" peak - which for a telescope would put the object in sharper focus. So I suppose it makes sense!
I checked that out and it definitely is the same concept, even if the profiles are not the same. Good to know!