John Hadley

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John Hadley

John Hadley (born  April 16, 1682 in Barnet , Hertfordshire , †  February 14, 1744 there ) was an English astronomer and mathematician .

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John Hadley became a Fellow of the Royal Society on March 21, 1717 . He found methods for grinding aspherical telescope mirrors , which enabled him to build the first powerful Newtonian telescope in 1721 . With its precise 15 cm parabolic mirror , it proved to be superior to a lens telescope of the same size. But he also built Gregory telescopes .

In 1731 he invented the octant , the forerunner of the sextant . In navigation and as a device for measuring star heights, it soon replaced the Davis quadrant used up until then .
His brothers George (1685–1768) and Henry (* 1687) were involved in the construction of the telescope as well as the octant, which was first named "Quadrant" .

The Mons Hadley , the Mons Hadley Delta and the Hadley groove on the moon, in the immediate vicinity of which the Apollo 15 lunar module landed, are named after John Hadley . In Graham Land in Antarctica, the Hadley Upland is named after him.


John Hadley was the oldest of George Hadley and Katherine Fitzjames' 6 children. His younger brother, George Hadley , became a well-known meteorologist and discovered the Hadley cells of the atmospheric circulation.
Hadley married Elizabeth Hodges in 1734. They had one child, John, born in 1738.

Same name:
His nephew John Hadley (1731–1764), son of Henry, chemist and doctor, member of the Royal Society from 1758.


  • EGR Taylor: The mathematical practitioners of Hanoverian England 1714-1840 . Cambridge 1966