Telescopes, Astronomical and navigational instruments, Herschel family, The Herschels as instrument makers, Optical equipment

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7-foot Newtonian (reflector) telescope

AST0960
Telescopes

Object details:

Object ID AST0960
Description This is a 7-foot Newtonian (reflector) telescope. The mahogany stand is on castors. Four motions: fine vertical and fine horizontal, two coarse vertical motions, one raising the front support, the other raising the tube behind, the tube resting in a rectangular frame running in grooves in the stand and the frame connected by a gut line to a handle. There is a round front cover held by three springs. A secondary mirror is in place with a cover and three adjusting screws held on a stem connected to a brass eye piece mount, itself with adjusting (focusing) screw and brass cover. A finder telescope is incomplete and attached to the side of tube above the eyepiece by a broken mounting. An objective mirror speculum (a type of metal) measures 6.3 inches. Accessories are in a drawer. William Herschel made and sold many telescopes of this type. He used his own 7-foot telescope (which would have been very similar to this one) with a 6.2 inch aperture magnifying images 227 times (depending on the eyepiece used), to make his 'second review of the heavens' in 1781 from his house in New Kings Street, Bath. It was during this review that he discovered the planet Uranus. Herschel was able to supplement the pension granted him by George III by making a number of these telescopes for sale.
Date made 1770-90

Artist/Maker Herschel, William
Place made Unknown
Credit National Maritime Museum, Greenwich, London
Materials brass; mahogany
Measurements Overall: 2134 x 197 mm
Parts
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