For 122 years, University of Illinois observatory has demystified the sky

URBANA – In 1896, when the University of Illinois Quad only had a handful of buildings, the school’s new observatory was part of the original South Farms, just north of the Morrow Plots.

“It was built on a little hill on the edge of campus,” astronomy professor Bryan Dunne said.

So it was really dark at night. Perfect for looking at the stars.

Now the observatory has neighbors in every direction, and you can see Champaign-Urbana’s light pollution from miles away on the highway.

Yet the observatory and its 12-inch refractor continue to work, although a motor has replaced rope as the method for moving the dome.

As Dunne pointed out, the observatory successfully has made the transition from a teaching role, mainly for mathematicians and civil engineers, to a few decades of enlightening experiments, and back to a teaching tool that helps its frequent visitors learn about the sky.

In the process, it has made a place on the National Register of Historic Places. More importantly, it’s a National Historic Landmark – a structure significant for the nation’s history, preservationist and U of I instructor Alice Novak said.

Right now, the 35-foot dome that’s mostly original, like much of the equipment, serves as a shield from a sunny day.

But it still is hot under that dome; to avoid distortion, the temperature of the equipment must match that of the air outside – in this case, about
90 degrees.

A clock inside measures “sidereal time” – the motion of the earth relative to the distant stars. So while the tour starts about 3 p.m., the sidereal clock shows a little past 5.

“The stars rise [and set] about four minutes earlier a day than by solar time,” Dunne said, adding that the observatory was able to measure time so accurately that the railroads once were willing to pay for it.

The observatory has a unique place in U of I history. The Urbana campus has had one since 1872, five years into its history.

In 1895, the state Legislature awarded $15,000 for the construction of an astronomical observatory for students.

“That was unusual; usually, these things are built with donations,” Dunne said.

The building cost $6,800 – less than its equipment. The 12-inch Brashear telescope, dome and other astronomical equipment cost $7,250, according to the astronomy department’s history.

That department didn’t exist then, Dunne said, and the teaching tool was mainly for the benefit of civil engineers in math classes looking to improve their surveying skills with knowledge they gained under the dome.

The builders were not fooling around, to read the landmark status nomination: “For maximum stability, [the telescope] is mounted on a brick pier, which extends down to bedrock and is not attached to the building in any way.”

After a few years of it serving as a teaching tool, professor Joel Stebbins turned the telescope into a vehicle for major research.

“By using electricity to empirically measure the brightness of stars, Dr. Stebbins revolutionized how astronomers gather data,” the astronomy department’s history said.

Stebbins was director of the observatory from 1903 to 1922.

“He made major advances in using photo-electricity to capture images,” Dunne said.

Stebbins and physics professor F.C. Brown built a photoelectric photometer that used electricity to measure the brightness of starlight, Dunne said.

“Before this, they took images on photographic glass plates that they ran downstairs to a darkroom and developed,” he said.

Today, U of I astronomers use telescopes in remote sites around the world, including Hawaii, the mountains of Chile, the South Pole, the back of 747s and even in space, Dunne said.

But that dome is here to stay.