John F. Gregory
Optical engineer who designed the Gregory-Maksutov telescope.
John F. Gregory (1927–November 14, 2009) was an American optical engineer who helped make telescope building popular among amateurs. He is known for creating a variant of the Maksutov telescope, now called the Gregory-Maksutov telescope.
Born in Cleveland, Ohio, in 1927, Gregory earned both a bachelor’s and a master’s degree in engineering from the Case Institute of Technology (today Case Western Reserve University). He started his career at Perkin-Elmer Corporation in Norwalk, Connecticut, during the 1950s. In the following decade, he worked at Barnes Engineering Company in Stamford, Connecticut, where he designed and tested lenses for infrared and ultraviolet applications. In 1974, he became chief engineer at the University of Texas McDonald Observatory. Four years later, he left to open Gregory Optics, a firm offering consulting, design, and fabrication services for optical and telescope equipment.
In 1957, Gregory published an article in *Sky & Telescope* titled “A Cassegrainian-Maksutov Telescope Design for the Amateur.” There, he explained how to build a version of the Maksutov catadioptric telescope that uses only spherical optical surfaces and features a small aluminized spot on the inner surface of the corrector lens as the secondary mirror. This design was simpler than the classical Maksutov and had the added benefit of keeping the secondary aligned, making the telescope more rugged. It also eliminated the need for a secondary support structure, which in other designs produces diffraction spikes in the image. Most Maksutov telescopes made today follow this approach, referred to as either a Gregory-Maksutov or a Spot-Maksutov.
Gregory’s article provided detailed optical specifications, shop techniques, and testing methods. He and others later published many more articles on the design in *Sky & Telescope*’s “Gleanings for ATMs” column, which eventually led to the 39-page pamphlet *Gleanings Bulletin C*. He went on to design a 22-inch f/3.7 Maksutov for the Stamford Museum and Nature Center in Connecticut, which remains the largest Maksutov in the United States. In 1980, he donated an 8.2-inch f/16 Maksutov-Cassegrain he had built to Case Western Reserve, naming it the “Nassau Memorial Telescope” after his former teacher, astronomer J. J. Nassau.
Quick Facts
- Birth Date
- 1927 · 1927
- Birth Place
- Cleveland, Ohio
- Death Date
- November 14, 2009 · 14 November 2009
- Death Place
- Austin, Texas
- Employer
- Perkin-Elmer Corporation
- Occupation
- Optical engineer
- Spouse
- Carolyn
Facts from the source article.
Lore & Background
In 1957, Gregory published an article in Sky & Telescope magazine titled 'A Cassegrainian-Maksutov Telescope Design for the Amateur.' In it, he showed how to construct a version of the Maksutov catadioptric telescope in which all optical surfaces are spherical, with a small secondary aluminized spot on the inner surface of the corrector lens. Gregory's design was simpler than the classical Maksutov and had the advantage of fixing the alignment of the secondary, eliminating the need for a secondary support that would otherwise cause diffraction spikes. Most Maksutov telescopes manufactured today are of this type, called either 'Gregory-Maksutov' or 'Spot-Maksutov.'
Gregory's article included detailed optical specifications, shop techniques, and testing algorithms. Many more articles by Gregory and others on his design appeared in the 'Gleanings for ATMs' column in Sky & Telescope, culminating in the 39-page pamphlet Gleanings Bulletin C. He later designed a 22-inch f/3.7 Maksutov telescope for the Stamford Museum and Nature Center, still the largest Maksutov in the U.S. In 1980, he donated an 8.2-inch f/16 Maksutov-Cassegrain he had constructed to Case Western Reserve, naming it the 'Nassau Memorial Telescope' after his former teacher J. J. Nassau.
Reader's Guide
John Gregory's 1957 design revolutionized amateur telescope making by making Maksutov telescopes simpler and more robust. His use of a secondary aluminized spot on the corrector lens eliminated the need for a separate secondary support, reducing diffraction spikes and improving image quality. This design became the standard for most Maksutov telescopes manufactured today. Gregory's detailed articles in Sky & Telescope, including specifications and testing methods, enabled amateurs to build their own instruments. His work at the University of Texas McDonald Observatory as chief engineer and later at his own firm, Gregory Optics, further contributed to optical engineering. The 22-inch f/3.7 Maksutov he designed for the Stamford Museum remains the largest Maksutov in the U.S. His donation of the Nassau Memorial Telescope to Case Western Reserve honored his mentor. Gregory's legacy is cemented in the widespread adoption of the Gregory-Maksutov design among amateur astronomers.
Did You Know?
- Gregory published his telescope design in a 1957 Sky & Telescope article.
- The Gregory-Maksutov uses a small aluminized spot on the corrector lens as the secondary mirror.
- He designed the largest Maksutov telescope in the U.S., a 22-inch f/3.7 for the Stamford Museum and Nature Center.
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