Engineering marvel: Sixth mirror cast for Giant Magellan Telescope

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When I was 10 or 11 or so (about 36 years ago) I was part of a leadership program in school, in Tucson. We got to do a full science tour of the U of A. My two strongest memories are of the laser labs and the mirror lab. I remember that the mirror they were working on, they said it took about 8 months to polish the 6 foot diameter surface. I didn’t know about their furnace at the time and we really only got to see the ‘front office’ (it was housed underneath the stadium)

scorpyo72

Perhaps someone knowledgeable in optics can explain why glass is used even in this case? It seems like a lot of complication comes from involving glass — has to be very pure, extra cautious handling. I also expect there is at least a slight double-image (as with our typical mirrors), though this can probably be factored-out in software. Maybe because glass is so much easier to shape… but then couldn’t it be used as a mold (as I’m guessing it effectively does for the reflective backing)? Maybe the structural value of the glass, by weight, is actually competitive? Or easier maintenance/cleaning? Perhaps it’s inertness… maybe a metal would need a coating in any case, which comes back to glass being the best choice?

glacialthinker

That’s so crazy

darkstarman

Will the James Webb be “better” because it’s in space?

0KdQ6

Peak heat day in the melt is today.

tugrumpler