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I think the answer to that is “not very much.” Telescopes use a lot of highly specialized parts made of rare and expensive materials. They use a lot of gold for

I think the answer to that is “not very much.” Telescopes use a lot of highly specialized parts made of rare and expensive materials. They use a lot of gold for various components and the mirrors are made of gold or platinum. The tolerances in the fabrication of the mirrors are EXTREMELY tight in order to reduce aberrations as much as possible. This sort of high precision manufacturing with exotic materials simply doesn’t scale.

denton-scratch 7y ago
"EXTREMELY tight" Telescope mirrors need to be polished to an accuracy of a quarter-wavelength of whatever radiation you want to capture - so for an optical telescope, that's a quarter-wavelength of visible light. Any greater precision than that is spurious, and won't get you better imaging. Less precision than that == bad mirror. The techniques for polishing and testing small mirrors (up to say 12") are amusingly low-tech, almost steampunk. You can get to 1/4 wavelength of visible light with a homemade grinding/polishing rig, and a homemade optical bench that consists of little more than a jig to hold the mirror, a lamp and a couple of razor blades. I'm sure the challenges in building accurate 30m optical mirrors are massively bigger, not least because very big mirrors warp under their own weight. But I imagine the principles are just the same. Incidentally, I had no idea people were building 30m ground-based optical telescopes; that's just insane. I mean, my house is only 8m high.