David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
Quote:All of the high-reflectivity mirror coatings use thin multi-layer overcoats of specific dielectric materials on top of a metal coating to get enhanced reflectivity over a regular metal only coating.
Quote:Since the incoming wave hits the primary mirror at a variety of angles (flat in the center and angled at the periphery), the nature of the coatings would have to be continuously variable from center to edge, That's not beyond the possibility of technology, just beyond the size of our wallets.
Quote:Well ok but I can get a 98% enhanced coating that's non dielectric yes? I'm not understanding why a guy would ruin secondaries if the same light reflectivity was had sans the stress.Why is dielectric around at all if its so temperamental?Thanks!Pete