Clark, Alvan

Clark, Alvan, 1804–87, American astronomer and maker of astronomical lenses, b. Ashfield, Mass. In 1846 the firm of Alvan Clark & Sons was established at Cambridgeport, Mass.; it became famous as the manufacturer of the largest and finest telescope lenses. The first achromatic lenses made in the United States were produced there. Clark's son,

Alvan Graham Clark, 1832–97, b. Fall River, Mass., became a partner in the business. Among lenses made under his direction are the 26-in. lens at the U.S. Naval Observatory, Washington, D.C.; the 36-in. lens at Lick Observatory, California; and the 40-in. lens at Yerkes Observatory, Wisconsin, which is the largest refracting telescope in the world. The younger Clark discovered a number of double stars as well as the companion star of Sirius.

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Clark, Alvan (1804–87) astronomer; born in Ashfield, Mass. A moderately successful portrait painter and engraver, he developed an interest in optics at age 40 when his son George was studying engineering. This led to the founding, with his sons George Bassett Clark (1827–91; b. Lowell, Mass.), and Alvan Graham Clark (1832–97; b. Fall River, Mass), of Alvan Clark & Sons, makers of optical lenses for telescopes, some of unsurpassed quality. His company represented the first significant American contribution to astronomical instrument making. They tested the lenses themselves, seeking difficult-to-find double stars. In 1862, Alvan Graham won the Lalande Prize for discovering the companion of Sirius.