Alvan Clark

Alvan Clark 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.

Clark, Alvan (1804–87)Americanoptician. His company at Cambridge, Massachusetts, made the lenses for the world's two largest refractors, the 36-inch (0.91-m) at Lick Observatory and the 40-inch (1.01-m) of Yerkes Observatory. In 1862 his son Alvan Graham Clark (1832–97) discovered the first white dwarf, the companion of Sirius, while testing an 18½-inch (0.47-m) Clark refractor.