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F&M's Historic Telescope Gets a Rare Cleaning

  • Andrea Lommen with the Clark Telescope
  • Astronomy Professor Andrea Lommen explains the Clark-Repsold Telescope's history. (Photo by Melissa Hess)

Peering into the heavens for more than a century, Franklin & Marshall College's rare telescope collected plenty of star data, but it also collected a lot of dirt.

This spring, nearly 127 years after the College opened its first observatory on June 16, 1886, the Clark-Repsold telescope had its lens taken apart and painstakingly cleaned.

"Its historical value is great," said Andrea Lommen, F&M's observatory director and an associate professor of astronomy. She noted there was concern in the department about the consequences of an overdue cleaning. "We had various consultants telling us, ‘You don't want to be the one to break a Clark telescope.'"

The telescope, which resides at the Joseph R. Grundy Observatory on F&M's Baker Campus, is primarily used for public viewings held on the third Monday of each month. 

    • Clark-Repsold Telescope
    • This photo shows the crystal clear glass once it has been returned to the cell. (Photo by Steve Spadafore)

    • Clark-Repsold Telescope
    • The sides of the lens are carefully taped down to keep dirty water from splashing on the underside of the lens as it is rinsed. (Photo by Melissa Hess)

    • Clark-Repsold Telescope
    • John Augustine stands with the Clark-Repsold telescope at the Grundy Observatory. Augustine refers to himself as an "antique telescope restorer and celestial engineer." (Photo by Steve Spadafore)

    • Clark-Repsold Telescope
    • To clean the lens, John uses a simple homemade dish soap solution to rinse the glass while brushing the lens with a soft paintbrush. (Photo by Melissa Hess)

    • Clark-Repsold Telescope
    • Custom-made jacks are used to lower the lens cell out of the telescope. (Photo by Steve Spadafore)

    • Clark-Repsold Telescope
    • Augustine brushes a ketchup treatment around the edge of the lens cell frame to loosen dirt and grime. (Photo by Steve Spadafore)

    • Clark-Repsold Telescope
    • A closeup image of the lens shows particulate dirt that has formed on the edges of the crown glass. (Photo by Steve Spadafore)

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Observatory staff members were motivated to clean the telescope's crown glass (curved lens) and flint glass (refractive lens to correct light distortion) after they discovered water droplets on the delicate lens over the winter.

"[Moisture] is bad, since it could promote mildew growth, which can then emit hydrofluoric acid that can etch the glass surface, thus damaging it," said Steve Spadafore, electronics engineer in F&M's Department of Physics and Astronomy.

Ed Cook, the observatory assistant who conducts the public viewings, noticed the droplets in February when he took a flashlight to peer inside the telescope. He said he could see a film over the lens and buildup of dirt particles around the edges.

Cook examined the lens after noticing some resolution issues when panning the night sky during one of the public sessions, which he's been overseeing since November.

"I just thought the image looked a little washed out," he said.

Since the lens cleaning, Cook said, the view of the sky has improved significantly. 

"It's sharper and darker," he said. "Space is black instead of being washed out."

In 1884, A. Repsold & Söhne of Hamburg, Germany, made the brass telescope for F&M at a cost of $4,199. The following year, Alvan Clark & Sons of Massachusetts crafted the lens for $2,200, according to F&M Archives and the book "Alvan Clark & Sons, Artists in Optics."

The telescope's 11-inch lens is rare. Only a handful exists, and the lens was one of the last made by Alvan Clark, according to "Alvan Clark & Sons."

Reluctance to clean the lens was assuaged when Cook did some research and tracked down John Augustine, an antique optical instrument specialist and retired fireman from Parkman, Ohio.

In 2012, Augustine cleaned the 15.5-inch lens on the University of Wisconsin's 130-year-old telescope. The university's observatory staff told him the lens hadn't been cleaned in nearly a century.

"I've had an interest in optics ever since I was a teenager," said the 63-year-old, a wiry antiquarian who has refurbished optical instruments as a career for 15 years.

Augustine arrived in early May with his custom-made precision riggings. He spent four days in a laboratory in the Hackman Physical Sciences Laboratories, where he gently separated the lens from the telescope assembly.

He soaked the lens in distilled water and dish detergent for 24 hours. Then he used a hose to shower the glass with water, using a soft brush and detergent. He dried it with compressed air, never touching the lens. He repeated this process three times.

Augustine cleaned the brass assembly with ketchup. "It's very gentle and it's slow working," Augustine said, explaining it doesn’t scour the metal. "It doesn't have any harmful effects."     

The telescope was last refurbished nearly half a century ago, in 1967, by the Wilmot Engineering Co. of Philadelphia, which installed two motors on the instrument so that it could track objects in the sky. Spadafore said the lens may have been cleaned at the time, but there is no official record of a cleaning.

When the Clark-Repsold went to Philadelphia for refurbishing, its home for 80 years, the Daniel Scholl Observatory, was razed for the construction of Hackman.

The telescope then found its new home at the Grundy Observatory on Baker Campus.

"It's a beautifully balanced telescope," said Lommen, who uses a radio telescope for her work but enjoys exploring the skies through the Clark-Repsold. "It still has one of the best optical systems anywhere."