Monday, December 30, 2013

Encouraging Mirror Figure News

If that subject line doesn't make sense -- that's okay.  The business rebuilding Big Bertha reports that the refigure of the mirror by Swayze Optical was apparently quite successful:
A "Steve Swayze" refigured mirror for Clay's 17.5" F4.5 telescope. A first look with the optics shows beautiful "tight" pin-point stars.
No doubt this is a great mirror!!
My guess is that DobSTUFF has seen a lot of telescope mirrors.  This makes me more confident that the $810 I spent having Swayze Optical refigure and recoat the mirror was well-invested.  I had never been completely happy with the optical performance of that mirror.  Swayze's report was that it had a turned edge, which confirmed what I already suspected.  I am hoping to improve on pictures like this:




Unknown said...

Are you planning for astrophotography with the Dob mount? Everything I've read says you need a tracking mount, but I'm wondering if short-duration video cameras and stacking/alignment software will allow more photography with simple mounts.

Clayton Cramer said...

Short exposures (1/8 second or less) don't require a tracking mount. There are platforms that provide up to about 20 minutes of tracking with a Dob, and that is on my list of things to buy.

Kirk Parker said...

Did they regrind the mirror, or just redo the coating?

Clayton Cramer said...

A turned down edge can't be fixed by recoating. But if they had to regrind it (meaning to use the coarse abrasives) that would have been pretty expensive. I am pretty sure that they only repolished the surface (that uses a 5 or 3 micron cerium oxide), then did the semimagical reparabolizing process, which is what is called figuring the mirror. I call it semimagical, even though I have done this myself long ago on a 3" f/4.5 mirror.