Telescopes were first constructed in the Netherlands about 1608.
In 1853 Alvan Clark
, of Cambridgeport, Mass.
, a comparatively unknown portraitpainter, after having experimented from 1846 in grinding lenses, succeeded in turning out a glass superior to any made elsewhere in the world.
He and his sons went on making large and larger instruments, till they ground the 36-inch telescope for the Lick Observatory
, in California
, and the son, Alvan G., made the 40-inch Yerkes
telescope for the observatory of the University of Chicago
, erected at Williams Bay, Wis.
The movable part of the latter, which turns on the polar axis, weighs about 12 tons, and the clock weighs 1 1/2 tons.
The refracting telescopes of the Naval Observatory
, at Washington
, 33 feet long, and at the Leander McCormick Observatory
, University of Virginia, both made by Alvan Clark
& Sons, have a 26-inch aperture.
The largest reflecting telescope in the United States
is at Harvard University, 28-inch mirror.
Other notable telescopes are at Princeton University (Clark
, 23-inch); Rochester, N. Y.
, 16-inch); Madison, Wis.
, 15.5-inch); Dudley
, at Albany, N. Y.
, 13-inch); University of Michigan
, 12.5-inch); and Middletown University (Clark