Well, I just tried this out visually on my Megrez 90 against my other masks, and have to say that it does definitely work as advertised. I was able to tell with precision where the critical focus zone was within at least 1/8 of a turn on my 10:1 Crayford focuser, even with my non-perfect eyes. It was so much better that, when the wind blew my old mask under the lawn mower, I didn't bother going after it
I do have one unresolved curiosity. I notice that a lot of people are using a circular mask to define the outside edge of their diffraction slits. The ends of these slits are not squared off, and I'm curious how much of an impact this will have on the diffraction pattern. Attached is the shape of the mask that I made.
Any comments?
Regards,
Eric