Today I was cleaning out my office. I’m a clutterbug: I have tons of treasures, but also, let’s face it, an even larger amount of crap. When I first moved to California 19 years ago, everything I owned fit in 13 banker’s boxes. Now, I don’t even think my power adapters would fit in 19 bankers boxes. So, I was ruthlessly going through boxes and tossing stuff out. Along with endless old cds, and papers that I printed out, I found a bunch of stuff from one of my previous obsessions: telescope making. I even found a 6″ mirror, aluminized, carefully wrapped in optical tissue. I’ve pretty much abandoned telescopes in recent years, but I really should get back into it again.

Anyway, tonight I was strolling down memory lane, and encountered a link to something I hadn’t seen before: the Bahtinov Mask. It’s a gadget that you can place in front of a telescope to help you focus precisely. It uses a very clever arrangement of masks to produce a diffraction pattern which can be adjusted to a precise focus.

If you dig around, you can find all sorts of testimonials about how terrific they are. I’ll have to make one of these and give it a try. Perhaps if I can find someone who will loan me a laser cutter, I’ll even cut a really precise one.

Addendum: Here’s a link to a nice mask generating program that will output an SVG file for any scope you need.