New Glasses for UNL Telescope
Technology sharpens vision of Behlen's 30-inch telescope From VISIONS Fall/Winter 1992
A hunk of Behlen Observatory's domed roof peels back like the eyelid on a sleeping giant. Gears spin through a slotted track and the rest of the roof turns like a wayward merry-go-round beneath the nighttime sky.
Ed Schmidt, UNL professor of physics and astronomy, is at the controls.
Picking up a pair of paddles similar to a television's remote control, he says, "In tile old days, we'd use these to turn the telescope until the numbers on the tracking instrument matched those in the catalogue."
Schmidt is at the base of the telescope. It's a stubby white barrel that slants to the open roof of a round-shaped room that feels like a turret in a medieval castle. From outside it looks like a farm silo. He pushes a button on one of the paddles and the telescope whirs and moves gracefully in response. The telescope moves less rapidly when he presses the button on the other paddle, and illuminated numbers on the tracking instrument slow down as Schmidt moves in on the precise fix on the slice of universe for which he is searching.
"Now we program computers to do the work, without any help to speak of from us," Schmidt said.
No more do astronomers stand next to the telescope for long hours on cold winter nights, as Schmidt has done many nights during his career. Now, he and his colleagues make their observations from a comfortable, climate controlled room at the base of a short winding staircase connecting the observatory with an adjacent building.
Schmidt points to a cone-shaped metal box bolted to the barrel of the telescope. "This is the heart of the telescope now?" he says. "It's called a CCD, which stands for charge-coupled device. We added it to the telescope in the mid 1980s with funds that included an $84,000 grant from the National Science Foundation.
"The CCD, a computer chip similar to those in small television cameras, 'pushes performance up' in the telescope," Schmidt says. The chip contains 250,000 tiny detectors that break down what the telescope sees into tiny bits of information called "pixels." These "pixels" are fed into a computer and their data eventually wind up as a picture on a television screen in the control room.
"Because of the CCD, we can observe a lot of stars that were too faint to see before," Schmidt says. "And," said Don Taylor, also a UNL professor of physics and astronomy, "we can cover a volume of space 100 to 1,000 times greater than we could before."
The CCD is the latest in a long line of improvements made to the telescope, mostly using in-house help, since the telescope went on line in 1972. Taylor is an astronomer with a flair for design and mechanics that he has demonstrated time and again over the years. He built many of the instruments used at the observatory, including a photometer for measuring brightness of objects through color filters, and a spectrum scanner for measuring the brightness of an object's spectrum wavelength by wavelength.
Kam-Ching Leung, another of Taylor's colleagues, came to the university in 1970 from NASA's Goddard Institute for Space Studies in New York because he "relished the challenge of building a good astronomy program where none previously existed."
"When I was still in Arizona," Taylor says, "Kam started sending me things and asking me what I thought. He had me write up the specifications for the telescope which were submitted to the company.
Leung himself was putting in long hours, developing an astronomy course curriculum and trying to find money to build an observatory and buy a telescope. Waiter D. Behlen, who had donated money to build Behlen Laboratory in the 1960s, agreed to put $160,000 left over from the Behlen project to be put toward the observatory project. He promised another $45,000 donation.
Originally, Leung planned to purchase a 24-inch telescope, but the availability of an unused building at UNL's Agricultural Research Center at Mead made it possible for him to put the money toward the purchase of a 30-inch telescope. The university also experienced savings on the telescope by joining the University of Washington in Seattle in choosing the same manufacturer, Bollen & Chivens, for its construction. Bollen & Chivens which has since merged with Perkin Elmer, the nation's foremost producer of quality telescopes, built telescopes for both universities, passing on cost savings to both universities as the result of the dual order.
The two-story building at Mead chosen for the observatory was originally a change house where people employed in the bomb factory active in World War II changed in and out of work clothes worn to handle gunpowder. Because its ground floor was built to double as a bomb shelter, it is an extremely sound facility, with first-floor walls built of high density reinforced concrete. The first floor remains unused hut the second floor provides plenty of space for offices, sleeping quarters, a display room, and the more recently completed computer room.
The total cost of the renovation and construction project, including the silo-shaped structure built from scratch that houses the telescope and the telescope itself, was about $300,000. From the start, Behlen observatory was regarded as the site of the best astronomical observing facilities in Mid-America. Today, with its CCD, it probably still is. The CCD enabled Behlen to match the capability of the 200-inch Hale telescope at Mount Palomar before Mount Palomar installed its own CCD.
The Behlen telescope is mounted on a concrete pier that extends down through two stories and another 10 feet below ground level to rest in a bed of sand. The original plan was to set it on bedrock, but bedrock here is so deep that the manufacturer recommended that the concrete pier be "floated" in sand to minimize vibration along the earth's surface as much as possible.
Schmidt and Taylor head down the curving stairs from the telescope to the adjoining structure.
"We don't have to be up here at all to make our observations," Schmidt says. "But I still come up here about every hour or so to check the temperature, which can affect the focus of the telescope. I also check the weather. It could be raining up here, and we'd never know it down in the computer room." The control room is crammed with electronic equipment and computers. Schmidt shoves a floppy disk into the slot of one computer terminal. The disk contains the telescope's previously planned tour of the skies for the night. The objective is to gather information about variable stars as part of a long-term project that requires that Schmidt drive 40 miles from Lincoln to the observatory two nights a week to gather data. He pays undergraduate students to make the trip three other nights per week.
Above, the telescope is swiveling, about to close in on the coordinates being dictated to it through the preprogrammed computer disk. When the telescope's sophisticated CCD instrumentation locks in on the star it's seeking, a picture will be taken and relayed to the screen of a second computer terminal, along with data on brightness and other characteristics that Schmidt has ordered. In the automatic mode, the telescope will track a number of stars over a period of several hours.
"The computer does most of the work," Schmidt says. "It's mostly a matter of keeping an eye on things to make sure that the telescope stays on track.
"The main thing that can go wrong is that it will miss a field by a wide enough margin that the computer isn't sure what star it's looking for. If it's not too far off target, it will make the correction itself, but sometimes we have to find the star we want it to focus on and direct it from the terminal.
Even in the automatic mode, observations can take several hours.
"That's all there is to it," Schmidt says. "No more groping around, working with a dim flashlight under the telescope. Down here, we can see what's going on, and we're not making mistakes because we're tired or freezing.
When the night's work is done, about 4 a.m., Schmidt will sleep the rest of the night away in living quarters adjoining the control room. While he sleeps, the computer keeps working. The computer won't make him eggs and bacon for breakfast, but by the time Schmidt heads back to Lincoln; the computer will have provided him with the bread and butter of his trade -- a floppy disk filled with data on some of the 2,000 variable stars in the northern hemisphere selected to be included in the survey. --RES