The George Observatory Celebrates Successful Gueymard Restoration

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The George Observatory re-opens the famous 36-inch Gueymard Research Telescope to the public after a lengthy restoration of its primary mirror.

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“You can see the images with your own eyes instead of on a computer screen like other telescopes,” said Peggy Halford, George Observatory Director.

The George Observatory is proud to re-open the famous 36-inch Gueymard Research Telescope to the public after a lengthy restoration of its primary mirror. A smaller version of the Hubble Space Telescope, the Gueymard still weighs about 10 tons, making it the largest deep space telescope of its kind available for both public use and scientific research. It is the only specialized Cassegrain model that chooses to use an eyepiece rather than a computer monitor.

“You can see the images with your own eyes instead of on a computer screen like other telescopes,” said Peggy Halford, George Observatory Director. “It gives you a much more personal experience.”

A Ritchey—Chretien design, it features hyperbolic primary and secondary mirrors which sharpen the image, eliminating the fuzzy edges around its center, what is known to astronomers as an off-axis coma. With optics this precise, the telescope brings to the naked eye the phenomena of deep space.

A couple of years ago, astronomers at the George Observatory began to notice the quality of images in the Gueymard was degrading. Views were clearer in the smaller, though still research-grade, 11-inch refractor attached to the Gueymard. While they knew something was wrong, they didn’t expect the adventure they would embark upon to restore it to its original power.

When they removed the primary mirror, the equivalent of “checking under the hood,” they found environmental pollutants built up in microscopic divots and fissures left on its surface after its original grind 50 years ago. Optical technology has come a long way since then; imperfections in contemporary optics are virtually absent, Halford said. The Observatory acquired the telescope from Louisiana State University, where it had stood in swamp-like conditions another 25 years prior to its installation in Brazos Bend State Park. Time and humidity had taken its toll.

The Museum sent the delicate 500-pound mirror to a coating company that did the simple things first — a bath and a new reflective coating — to try to refurbish the mirror, but the coating refused to stick, and they knew they would need to bring in the “big guns.”

It took a three-month fundraising campaign, Save Our Scope, to raise the money to hire Master Optician James Mulherin to resurface the element. The campaign took much less time than anticipated, given the surprising amount of support from the public.

February 2014, the George again sent mirror away, this time to Mulherin, and a year and a month later, the project is complete. Mulherin recently took a trip to the George to help install the element. See video of the install here.

“It was a fairly routine job,” said Mulherin, whom universities and aerospace companies regularly hire for their optical needs. “There was no real challenge.”

Mulherin did mention, however, that he had to work around the hole in the middle of the mirror, where a steel hub goes through to hold the mirror in place at the bottom of the telescope. Normally a glass plug is installed during the grinding phase, but there was too much difference in the composition of this 50-year-old glass and that of contemporary optics, he said, so he had to work around it.

Using specialized equipment to move the delicate, but massive, hunk of glass, Mulherin’s company stripped the aluminum finish and ground down the old surface to remove the imperfections in the element. The opticians then re-shaped the mirror’s hyperbolic curvature, shining light through the glass at different stages to check their progress. Finally, Mulherin coated the surface with enhanced aluminum to increase reflectivity.

About the telescope, he said, “It’s amazing to me that it still works.”

Over 270,000 students have viewed through the Observatory’s telescopes, including groups from Australia, Scotland, the UK and International Space Schools. For more information on the Observatory and the past S.O.S campaign, visit our website at http://www.hmns.org or call (713) 639-4629.

The Houston Museum of Natural Science—one of the nation’s most heavily attended museums—is a centerpiece of the Houston Museum District. With four floors of permanent exhibit halls, and the Wortham Giant Screen Theatre, Cockrell Butterfly Center, Burke Baker Planetarium and George Observatory and as host to world-class and ever-changing touring exhibitions, the Museum has something to delight every age group. With such diverse and extraordinary offerings, a trip to the Houston Museum of Natural Science, located at 5555 Hermann Park Drive in the heart of the Museum District, is always an adventure.

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