Editor's note: The following is an excerpt from A Grand and Bold Thing: An Extraordinary New Map of the Universe Ushering In a New Era of Discovery by Ann Finkbeiner (on sale August 17 from Free Press). The book chronicles the development of the Sloan Digital Sky Survey, an influential astronomical survey that has charted the position of hundreds of thousands of galaxies and turned up large numbers of distant quasars. The excerpt below details some of the problems encountered by Princeton University astronomer Jim Gunn, the project's leader, and "French" Leger, an engineer at the University of Washington in Seattle (UW), in preparing the telescope at Apache Point Observatory in New Mexico for the survey.
One item on the observers' checklist was to inspect for moths. Apache Point called them miller moths—later research revealed them to be the adult form of the black cutworm—and every spring in New Mexico, they migrate to high elevations. During a bad year, Apache Point buildings could have hundreds of moths a day. Moths like dark, tight spaces, including the insides of electronic devices and the drives of telescopes. When the telescope moves, the moths are crushed on the drive surfaces, and the telescope slips or loses track of where it is. So the telescope drives had to be cleaned during times when observers had better things to do. "The moths cause us all kinds of hell," said French.
A college student interning with the UW engineers was commissioned to investigate moth-ejection measures. The moths were most active during hailstorms and seemed agitated by jingling keys. So the UW student, who had a scientific bent, smacked the walls and floor, then stomped and clapped, but the moths showed no sign of being annoyed until the racket was a few inches away. Then he aimed a speaker at a group of moths and broadcast sounds in a wide range of frequencies. At 0.4 kilohertz, the moths startled but settled back down; at 0.6 kilohertz, one moth moved briefly; at all other frequencies, the moths remained unconcerned. Then he tried shining beams of both incandescent and fluorescent light by turns on the group, and they all moved to the edge of the light. He turned the light off and back on again and forgot it until the next morning, when he found that the moths hadn't moved at all. Next, following advice from Apache Point veterans that blowing air seems to profoundly disturb moths, he proposed what he called a conceptual deterrent system that involved an air gun, small rubber tubing, a valve, and an electric timer. He built the system and blew jets of air at the moths; they tended to hunker down and wait until the jet was over. He was impressed that they could handle upward of 80 pounds per square inch, though they became restless with as little as 20. He installed this air-jet blowing system on the telescope and while it was working, no moths were run over—implying, he thought, some degree of success.
Further research found that, as French said, "interrupted air blasts they do not like." Eventually he built a moth ejector system that blew air intermittently through pipes with holes along their sides: "A 2 hertz puffer system is what we found to be most effective." He mounted the system on the most sensitive parts of the telescope, and though the moth problem didn't completely resolve, it was much improved.
The telescope's real problem was the one that had made first light so nearly frustrating: it couldn't point. The observers would type in the coordinates on the sky and hit Enter, and the telescope was supposed to go to those coordinates immediately. Night log May 29, 1998: "Another clear night. We aimed to fill in the stripe of the data we took last night. In order to do this, we had to obtain the current position of the telescope. We got on the sky at 9:10 p.m.; we had a position at 11:15 p.m."
Or they'd try to find a kind of star with standard and known brightness, called an FK5 star. Night log May 16, 1999: "We were unable to acquire our field. We were then unable to acquire an FK5 star. We were then unable to acquire Arcturus." The pointing was 3 arc minutes off, a tenth of a moon off, and the telescope was aiming at something that was an arc second across. The observers that night were Chicago and Princeton postdocs, and the Chicagoan, Scott Burles, wrote the night log: "At 1 a.m., we found Arcturus and returned to our FK5 star. We chased the fast and wily FK5 star for several hours." "Fast and wily" is a joke; no FK5 star is anything but steady and predictable. "Can't wait to get up in six hours and do this all over again," he wrote.