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objects above the horizon at sea. A mobile arm carrying a mirror and pivoting on a graduated arc provides a reflected image of the celestial body overlapping the image of the horizon, which is observed directly. If the position of the object on the sky and the time of the observation are known, it is
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He died in East Barnet in 1744 and is buried in the local churchyard with other members of his family. He had married
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In 1730 Hadley invented the reflecting octant, which could be used to measure the altitude of the sun or other
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Biography from the School of
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Institute and Museum of the
History of Science, Florence, Italy: Picture of Hadley's octant
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to the Royal
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In 1717 John became a member (and later vice-president) of the
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Hadley also developed ways to make precision aspheric and
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The complete
Amateur Astronomer - John Hadley's Reflector
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Henry C. King - The history of the telescope - page 77
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List of largest optical telescopes in the 18th century
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and his wife
Katherine FitzJames. His younger brother
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mathematician, and laid claim to the invention of the
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Correspondence between
William Penn and James Logan
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390:telescopeѲptics.net - 8.2. Two-mirror telescopes
300:. Philadelphia: J. B. Lippincott & Co. 1870.
116:(16 April 1682 – 14 February 1744) was an
357:amazing-space.stsci.edu - Hadley’s Reflector
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424:King, H.C. (1970–1980). "Hadley, John".
221:. In 1721 he showed the first parabolic
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191:easy for the user to calculate his own
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229:, compared favorably with the large
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219:reflecting telescopes
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262:Ponders End
260:Academy in
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250:Rima Hadley
246:Mons Hadley
150:East Barnet
114:John Hadley
94:Nationality
83:East Barnet
32:John Hadley
461:Categories
284:References
138:Bloomsbury
61:Bloomsbury
53:1682-04-16
215:objective
212:parabolic
188:celestial
132:Biography
404:Archived
331:15 March
272:See also
201:American
193:latitude
314:. 1885.
252:on the
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241:Honors
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142:London
122:octant
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65:London
199:. An
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