Shortly after, we had one of our astronomers go to the MMT and observe one night when a cold front went through. He was in constant phone communication with other observers at Kitt Peak, about 50 air miles away, and when the cold front came through, he said, “Oh, the images here have got much worse, very abruptly”, and the Kitt Peak astronomers reported that theirs had too. About an hour later the images got much sharper at the MMT, and he contacted Kitt Peak and said “Our images have sharpened up, what about yours?” and the answer was “No, ours haven’t.” The images stayed fuzzy at Kitt Peak for days after that.

New Multiple Mirror Telescope: In the new design for the mirror, the honeycomb structure of the segments lies beneath a smooth coating.
Credit: Steward Observatory Mirror Lab

And this is because all of the mirrors in the telescope at Kitt Peak were the regular thick glass mirrors, but at the MMT the mirrors had been obtained from the Air Force: they were intended for space use and they were lightweight to save money at launch so you never had more than a fraction of an inch of silica cooling to the air, thus the mirrors could adapt to changing temperature very rapidly. With thick mirrors, air turbulence is created in the light path when the residual heat of the mirror comes into contact with cooler air. The turbulence spoils the images until the mirror cools down some days later.

We understood this, and started discussing among ourselves how one would make the next large telescope, and benefit from this understanding, so it would have very sharp images, and it was that which finally led to Roger Angel developing the Mirror Lab. I worked very closely with him all the way, even though he’s much better at technology than I am. And yet, at times I had ideas that he didn’t, though he certainly is a very, very creative person.