On Wed, 2012-10-03 at 13:03 -0400, Kent A. Reed wrote: > On 9/30/2012 11:45 PM, Kirk Wallace wrote: > > I'm playing with the thought of putting a vacuum deposition system > > together to coat telescope mirrors with aluminum. It looks like I could > Kirk: > > I forgot to ask. What's the biggest mirror you contemplate coating?
The cost of a glass blank is the limiting factor. I'd like to use borosilicate glass and I probably can only swing a 12" if a really good deal comes along. I'm hoping that by planning out much of the details for the mirror and vacuum system, I can take advantage of really good (maybe even free) deals as they come along. I've even given some thought to making my own blanks: http://www.mdpub.com/scopeworks/index.html http://www.mdpub.com/ > On the one hand, that's a technical question since it affects the sizing > of the vacuum chamber, vacuum pumps, and the coating mechanism, and also > affects one's ability to coat the mirror uniformly. I'm thinking of using a flat plate for a chamber base on which I can place different sized chambers. I suspect the limit to chamber size will come from pump size, pumping time and the amount of leakage. I'm expecting I'll upgrade parts of the system as I go, but I'm shooting for accommodating a 12" mirror with a eye towards 20". I really want what Drew made on page 8 here: http://www.altazinitiative.org/Word%20Documents/PdfsLBConf.2010/Hawaii.LBA2010-11.FoamGlassCompositeMirrors-Aurigema.pdf Finding a re-buildable vacuum system in a dumpster would be good. http://www.ebay.com/itm/370658381398 > On the other hand, it's purely personal curiosity. My long-ago partner > in astronomical crimes and I never managed to grind anything bigger than > an 8in dia. mirror for a classic Newtonian reflecting telescope. The > optical figure wasn't great and we used wet chemistry to silver the > mirror so it wasn't so great either. Fortunately, the seeing conditions > in and around Albuquerque, New Mexico in the late-1950s, early-1960s > were superb and even our crappy scope could give us a number of thrills. > > Regards, > Kent I am sending a 6" mirror from a Criterion RV-6 http://www.philharrington.net/old60.htm (about a third of the way down) that I rescued in pieces from a junk pile to be re-coated in a couple of days. http://alcoat.net/al_4.htm The mirror worked pretty well even with 40 years, and bird and spider droppings removing some of the coating. I am also finishing up the mirror my father started in the 60's. I've started figuring and put the uncoated mirror in the Criterion tube and got good views of the Moon and some of the brighter stars. I didn't expect much since the Foucault tests looked pretty rough. I used the de-coated Criterion as a reference and the Foucault images looked perfect except a tiny tiny bit of ripple in the center which is mostly covered by the the secondary mirror. I'm waiting for more pitch and rouge to finish my father's mirror, then it's off to the coater. I'm at 3000ft on the East side of California. Most clear nights I can faintly see the Milky Way by eye, but I think the Moon phase is the biggest factor here, occasionally, it really stands out. With the yucky Criterion mirror I could just make out the Andromeda galaxy. I'm hoping the new coating will improve this. http://en.wikipedia.org/wiki/Andromeda_Galaxy -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Don't let slow site performance ruin your business. Deploy New Relic APM Deploy New Relic app performance management and know exactly what is happening inside your Ruby, Python, PHP, Java, and .NET app Try New Relic at no cost today and get our sweet Data Nerd shirt too! http://p.sf.net/sfu/newrelic-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
