Alvan Clark

Alvan Clark (March 8, 1804 – August 19, 1887), born in Ashfield, Massachusetts, was an American astronomer and telescope maker. Using glass blanks made by Mantois of Paris his firm, Alvan Clark & Sons, ground lenses for refracting telescopes, including the largest refracting telescope in the world, the 40-inch at Yerkes Observatory, and the second largest, the 36-inch telescope at Lick Observatory. One of Clark's sons, Alvan Graham Clark, discovered the dim companion of Sirius. His other son was George Bassett Clark; both sons were partners in the firm.

Craters on the Moon and on Mars are named in his honor.