Alvan Clark & Sons
Alvan Clark & Sons was an American maker of optics that became famous for crafting lenses for some of the largest refracting telescopes of the 19th and early 20th centuries. Founded in in Cambridgeport, Massachusetts, by Alvan Clark (–, a descendant of Cape Cod whalers who started as a portrait painter), and his sons George Bassett Clark (–) and Alvan Graham Clark (–).[1] Five times, the firm built the largest refracting telescopes in the world. The Clark firm gained "worldwide fame and distribution", wrote one author on astronomy in [1]
The inch (&#;mm) Dearborn telescope (housed successively at the University of Chicago, Northwestern University and Adler Planetarium) was commissioned in by the University of Mississippi. The outbreak of civil war prevented them from ever taking ownership. As a result, it was being tested in Cambridgeport when Alvan Graham observed Sirius B in
In they built the inch (&#;mm) objective lens for the refractor at the United States Naval Observatory. In , they build the inch (&#;mm) telescope for the Pulkovo Observatory in Russia, the inch (&#;mm) objective for the refractor at Lick Observatory was made in , and t
Scientist of the Day - Alvan Graham Clark
The Yerkes inch refractor, built by Alvan Clark & Sons, on display at the World’s Columbian Exposition, Chicago, , photograph ()
Alvan Graham Clark, an American lens crafter and telescope maker, died June 9, , at age Alvan Clark, his father, was a pioneer in the building of large refracting telescopes (telescopes with lenses, not mirrors), and Alvan Graham, with his older brother, George Bassett, followed his father into the business, which was based in Cambridge, Mass. The three of them produced the largest and finest refractors ever built, including the inch refractor for the U.S. Naval Observatory (USNO) in Washington, D.C. (with which Asaph Hall discovered the two moons of Mars in ), and the inch refractor for Pulkovo Observatory, near Saint Petersburg, commissioned by Otto Wilhelm von Struve, who came all the way from Russia to Cambridge to meet the Clark family and see for himself what they could do with a pair of large glass blanks (inch and inch refers to the diameter of the glass lenses, which were usually made as doublets, one lens concave and one convex, to prevent chromatic aberration). You can see photos of t
(Pictured on left, father in middle, brother on right)
Alvan Graham Clark was born on July 10, in Fall River, Massachusetts. He was the son of Alvan Clark and Maria Pease Clark; he had an older brother named George Bassett. His father started out as a calico engraver and portrait painter, but eventually developed an interest in the production of telescopes. George Bassett, a science student in , tried his luck at casting and grinding to create a reflecting telescope lens with his father&#;s help; their lack of success led them to attempt the onerous task of a refractor. After a look at Harvard College Observatory&#;s great refracting telescope, as well as its price despite the obvious flaws in the glass, they began making and selling telescopes. By , the Alvan Clark & Sons firm was founded.
Alvan Clark & Sons become known for their manufacture of large telescope lenses of excellent quality. Treasured by collectors and amateur astronomers are their more modestly-sized equipment. Between and , they made the lenses for: inch at Unit
40" telescope at Yerkes
40" telescope at Yerkes |
Alvan Clark & Sons finished the lens (actually an achromatic pair, one lens of crown glass and one of flint glass) in October It weighed pounds and had a focal length of 62 feet. In , the lens was shipped to Williams Bay, Wisconsin, the chosen site of the new observatory. The telescope with its moving parts and counterweights weighed over 20 tons, yet it was so well-balanced that small motors could easily move it to point at any part of the sky. As at Lick, astronomers could raise and lower the entire floor of the observatory in order to reach the eyepiece. Astronomers who used the new telescope were delighted with its quality.
Hale meant to devote Yerkes Observatory to a relatively new branch of astronomy, astrophysics. Breaking with the established classical astronomers, who mainly concerned themselves with the positions and movements of the stars and planets, Hale was determined to promote the study not just of how celestial bodies moved, but of what in fact they were.
Hale's ambition is reflected in the architecture of Yerkes Observatory. The giant inch telescope was n
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