Alvan Clark & Sons was an American maker of optics

Optics

Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...

 that became famous for crafting lenses for some of the largest refracting telescope

Refracting telescope

A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an image . The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long focus camera lenses...

s of the 19th and early 20th centuries. Founded in 1846 in Cambridgeport, Massachusetts by Alvan Clark

Alvan Clark

Alvan Clark , born in Ashfield, Massachusetts, the descendant of a Cape Cod whaling family of English ancestry, was an American astronomer and telescope maker. He was a portrait painter and engraver , and at the age of 40 became involved in telescope making...

 (1804–1887, a descendant of Cape Cod whalers who started as a portrait painter), and his sons George Bassett Clark

George Bassett Clark

George Bassett Clark was an American instrument maker and astronomer.Born in Lowell, Massachusetts and educated at Phillips Academy, Andover, he was the son of Alvan Clark, part of a family of refracting telescope makers in the 19th century...

 (1827–1891) and Alvan Graham Clark

Alvan Graham Clark

Alvan Graham Clark , born in Fall River, Massachusetts, was an American astronomer and telescope-maker. He was the son of Alvan Clark, founder of Alvan Clark & Sons....

 (1832–1897). Five times, the firm built the largest refracting telescopes, Great refractors, in the world.