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Hull, who worked on the project with Mark Kutney, an architectural conservator for Facilities Management, said historical astronomy expert Fred Orthlieb, the retired Isaiah V. Williamson Professor of Civil and Mechanical Engineering at Swarthmore College, studied the dome and the rollers and made a recommendation.

“He told us the rollers, which were pretty much original to 1884, were going bad,” Hull said. “They have these little cylinder ball bearings inside of them and over time they were getting bent out of round. Basically, the only way to fix it was to replace those rollers.”

Jimmy Davidson, the observatory’s instrument and laboratory technologist, led the project. He and Hull worked with Peter Dow, a machinist for the astronomy department who builds instruments from plans drawn up by the faculty and graduate students and maintains and repairs mechanical problems with the department’s telescopes. Dow and Davidson took training to operate a hydraulic lift, as well as harness and safety training, to work on the outside of the dome.

“The original rollers were basically just large roller bearings, but the rollers inside were worn down to the point that they were twisting and jamming,” Dow said. “Our goal was to keep as much of the original design as possible, while also bringing the moving components up to modern standards and making it easier to work on in the future.

“The rollers themselves, originally an odd 3 1/16 inches in diameter, were replaced with standard 2½-inch yoke rollers with modern bearings so that any subsequent replacements should be easy to source,” Dow said.

The original custom-built rollers were designed to fit very precisely in their steel track.

“They were made to such a close fit with the tracks that when the tracks were painted, the paint thickness was enough to cause the rollers to rub against the top painted surface of the track,” Dow said.

The Department of Astronomy kept the existing tracks but modified them with a stainless-steel track on which the bearings roll.

“This smaller roller allowed space for the stainless steel track along with clearance above to allow space for future paint and eliminate rubbing on the top track,” Dow said. “The tracks themselves were abated to remove the lead paint and primer, sandblasted – which exposed the original ‘Carnegie Steel’ stamp – and recoated with a modern protective system that is frequently used on steel in saltwater marine applications to give the maximum possible service life.”

The original tracks were hot-riveted to brackets on the dome and these tracks were reattached with nuts and bolts so that they can be easily removed in the future.

The original design also made it impossible to replace a roller without removing the entire track assembly.

“Due to age and corrosion, we had to destroy the roller we removed during our exploratory work in order to get it off,” Dow said.

The telescope – donated by Leander J. McCormick, who managed the manufacturing department of the McCormick Harvesting Machine Company (later International Harvester), which he owned with his brother, Cyrus, who was credited with inventing the mechanical reaper – has a 26-inch refracting lens crafted by Alvan Clark and Sons of Cambridgeport, Massachusetts. When it was dedicated on Thomas Jefferson’s birthday, April 13, 1885, it was considered one of the best telescopes in the country. The McCormick telescope was retired from active research in 1994 and today is used for education and public outreach.

“In terms of education, our undergraduate and graduate astronomy majors use the telescope in their classes on observational techniques,” Murphy said. “Students taking introductory astronomy for non-science majors also complete labs at the telescope each semester.

“In terms of public outreach, we offer the Public Night program, where the telescope is open to the general public on the first and third Friday evenings of each month, and to educational groups with advanced reservations on the second and fourth Fridays of each month.”

The observatory also hosts educational groups in the evenings and school groups during the daytime and offers professional development programs for teachers and summer programs for middle and high school students.

“Unfortunately, our public nights and outreach programs are on hold during the pandemic,” Murphy said.