Alvan Clark
Alvan Clark ( born March 8, 1804 in Ashfield, Massachusetts, † August 19 1887 in Cambridge, Massachusetts) was an American astronomer and telescope builder.
Clark founded the firm Alvan Clark & Sons, which specialized in the manufacture of lenses for the construction of Refraktionsteleskopen. The glass he moved from Paris. Some of the largest telescopes in the world to go back to his company. Among the world's largest at the Yerkes Observatory, the second largest at the Lick Observatory and the refractor of the observatory Pulkowa. Overall, Clark's company built five times represent the largest refractor in the world.
One of his sons, Alvan Graham Clark, discovered a companion of Sirius, his other son, George Bassett Clark, was a partner in the company.
A crater on the Moon and on Mars were named after him.