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Astronomy In California 1850 – 1950:
Telescope Makers, Telescopes, and Artifacts
Ritchey Reflecting Telescope
By George W. Ritchey, American Telescope Maker
George Willis Ritchey (1864-1945) built the first large, successful American reflecting telescopes. A telescope designer who perfected the methods for making astronomical mirrors, and a master of celestial photography, Ritchey worked closely with George Ellery Hale, a phenomenal fundraiser and organizer of observatories. Mount Wilson Observatory with its 60-inch and 100-inch reflector telescopes stands as a monument to their collaboration. But before the Mount Wilson telescopes, Ritchey built an important telescope at the Yerkes Observatory in Wisconsin.
The most important instrument built by George Ritchey at Yerkes Observatory was the 24-inch reflector in this exhibition. He made the primary mirror (a short focal ratio f/4 paraboloid) in his shop in Chicago, and in June 1898, sold it to the Yerkes Observatory for $200. Ritchey's assistant at Yerkes, Francis G. Pease, worked on the Cassegrain secondary mirror for the telescope, and Ritchey was using the telescope as a finished instrument two years later, set up for photography as a Newtonian reflector.
Ritchey's first published papers reporting results with the 24-inch were on his photographs of the "new" star Nova Persei, which had suddenly flared in brightness and appeared in February 1901. Ritchey later photographed many nebulae with the telescope.
These pictures provided astronomers the first opportunity to see the true forms and complicated structure of objects like the Orion Nebula, the Trifid Nebula, and the other nebulae that we are so familiar with today. But more importantly, these photographs convinced astronomers that reflectors, not refractors, would be the large telescopes on which future research would be based. After Ritchey's work with the 24-inch and James Keeler's work with the 36-inch Crossley reflector at Lick Observatory, no serious astronomer suggested building larger refracting telescopes, only reflectors. At this time, the Yerkes 40-inch refractor was already in operation, and became the last of its kind.
The 24-inch reflector became the prototype for the 60-inch and 100-inch reflectors that Ritchey would later build for the Mount Wilson Observatory in Southern California.
The telescope is of the German type equatorial mount. The primary mirror is silvered glass, 23 1/2 inches wide, by 2 5/8 inches thick at the edge. The bottom is supported at three points and at the edge. The skeleton tube, about 7 feet long, held the secondary mirror and photographic accessories. The diagonal now present is roughly oval, 7 7/8 inches long, 6 inches wide, and about 1 inch thick. The eyepiece position has an elaborate stage (brass) with a 2 1/8 inch threaded opening. The entire stage (graduated 360 degrees, by degrees) can be rotated, as well as moved precisely on either axis. The holder appears to be designed for use with a photographic plate apparatus. The drive mechanism is in the rectangular base. It consists of two electric motors, one providing primary motion and the other apparently used to make corrections while the first is running. The entire instrument is now painted gray.
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