Hand shapeing telescope mirror VS machined mirrors

[Calvin19 0]

So, i am halping my GF shape the mirror for her telescope, an 8" reflector. and we both have heard and read that a human can shape a lense so that it works better than the lense a machine shapes. I am really wondering how that works, i understand that a machine gives a repetatrive input, and a humans varies, and this can make the lense more 'perfect' than a machine can, but it still amazes me that a machine cannot make an actual 'perfect' mirror. it is not terribly complex, a telescope mirror. sigh. its going to keep me up nights.

-SPACE-

[Kris 0]

Umm... I think you heard wrong.

There are a number of telescopes (including the new Great Magellan Observatory) that are using clusters of 8.4 meter mirrors from the Mirror Lab at Steward Observatory in Arizona.

Currently, they polish the mirror to a surface smoothness that is within 25nm. 25nm is roughly equivalent to 75 hyrdogen atoms stacked on top of each other. So, no, you can't get that precision with hand polishing.

Steward Observatory Mirror Lab FAQ

If you go to thier home page, you can see an image of a mirror being polished.

Sky, Muff Bro, Rodriguez Bro, and
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[Calvin19 0]

maybe i did hear wrong. the point my astronomy instructor had made sense, but he could be wrong, but he is the CU instructor (gf's, not mine) ill ask him.

-SPACE-

[piisfish 140]

try asking Greg Gasson

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[mrGuy 0]

grinding and polishing your our mirror is time-consuming, frustrating, and very rewarding. But don't expect to reproduce the perfection of todays' machined mirrors.

I've built my own Newtonian Reflector from scratch; but not the mirror. There are hard core home builders still out there, and they are interesting to meet and talk to, but they usually get more pleasure in building than using.

Which type is your Girl Friend?

[JackC 0]

I used to work for a company that manufactures very high quality optics and the short answer is it depends on the man and the machine.

A very experienced and highly skilled man with the right equipment can make optics more accurately than your average run-of-the-mill CNC machine. But if you want the absolute best, you need a million dollar magnetorheological fluid lens grinding machine. Joe Bloggs in his shed with some wet'n'dry and a tube of Autosol wont get close.