This is actually on topic, but I wasn't sure where else to put it. Did anyone see this special on PBS? It was about George Ellery Hale and the building of the Hale telescope on Mt. Palomar. Hale was a tireless visionary and fundraiser who was able to persuade such big pockets as Yerkes and Carnegie to pony up the $$ to build the greatest telescopes on earth.
It was a 90 minute special, so I can't summarize it all, but the most astounding thing, to me, was that the opticians who worked on the 200" mirror actually used their thumbs during the final polishing. Apparently just rubbing your thumb across Pyrex will take off about 1,000,000th of an inch!!
The mirror is so perfect that, were it blown up to the size of the continental US, the largest dimple or bump would be no larger than a molehill!
Amazing achievement!