What does this mirror do?
January 7, 2012 10:22 PM   Subscribe

What is this giant reflective thing?

This object appears to be 4" thick by 16" across. It is mirrored on its top surface (unlike most mirrors, which have the mirrored surface under the glass). It has brackets. What is it? Provide a link to something similar, if possible.
posted by sarling to Technology (9 answers total) 2 users marked this as a favorite
First surface mirrors are used in optics inside cameras and telescopes
posted by hortense at 10:31 PM on January 7, 2012

My first thought is a telescope mirror, but that's a guess.
posted by empath at 10:32 PM on January 7, 2012

Best answer: Yeah, pretty sure it's a telescope mirror. Here's a larger one that is somewhat similar. And a smaller. The one in your photo is a lot older.
posted by iconomy at 10:38 PM on January 7, 2012

I always knew them as "front-silvered." If it's flat it may just be a lab mirror, too, with the brackets for filters or beam splitters or whatnot.
posted by rhizome at 10:58 PM on January 7, 2012

If it is slightly dished on the silvered side, so that it magnifies whatever is reflected in it, then yeah, it's a telescope primary mirror. Technically, you want to be very careful about touching the silver surface, but given the rust on the mount, it's probably due to be resilvered anyway.

The magic phrase for Google is "Newtonian Telescope".
posted by Kid Charlemagne at 12:28 AM on January 8, 2012

There's no discernable curvature in the image, so I'm guessing it's a flat.

It's also very thick for its size. Is it solid glass throughout?

Since it's just a flat mirror, it could be used for basically anything. We're going to need a little more context to figure out why this particular mirror exists. Where was it found? Is there other associated stuff? Even knowing a city would help. Is it near an observatory or physics department?

It actually reminds me of these mirrors on the solar telescope on Kitt Peak.
posted by kiltedtaco at 7:49 AM on January 8, 2012

Yep, telescope mirror.

This mirror is in for silvering, on the top surface. It has a hole, because it's a Cassegrain design, but yours could be designed to be used in a Newtonian or Dobsonian telescope.
posted by BrashTech at 10:06 AM on January 8, 2012

+1 for telescope mirror. A 16" piece of glass like that is not cheap. Be careful with it.
posted by jeffamaphone at 12:44 PM on January 8, 2012

Plus, think of all the bad luck if you break it.
posted by rhizome at 3:10 PM on January 8, 2012

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