I had a chance to look through Christine at Fremont Peak State Park (Calif). While I didn't do an extra focal test on a star, the in focus images were very nice.
Christine's owner seemed like a really nice guy. Christine is a work of art. At least he gets out and observes with his scope.
Rich
------------ ORIGINAL ATTACHMENT -------- SENT 08-18-95 FROM SMTPGATE (gag1@psu.edu)
> I recently corresponded, via email, with the author of the "Christine"
> article in the current Sky and Telescope. He wrote that he obtains much
> better than 0.001" repeatability on the Foucault test - even on center
> zones.
That's hard to believe. I'm doing real good if I can get .003 repeatability. (fixed light source) Typically, I often see differences of .005 (or more) between readings if I move the focualt tester just a bit. (I often do this so it's not so easy to "cheat" when doing the second set of measurements) Only by averaging together several sets of readings do I feel like I _might_ be getting readings accurate to .003" or so. And this is only at the edge - near the center it's nowhere near that good.
The funny thing about this is that if his testing is really that accurate, it's probably wasted anyway... He mounted that 12.5" mirror on THREE blobs of silicone sealant. No 9-point floating mirror support! ________________________________________________
Greg Granville - N3SPE - (day)814-865-3310 ARL-PSU gag1@psu.edu (eve)814-339-7244