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Hadley, John

Born: 1682 AD
Died: 1744 AD
Nationality: English
Categories: Inventor, Mathematicians

1862 – Born on April 16th in Hertfordshire, England. British mathematician and inventor who improved the reflecting telescope, producing the first such instrument of sufficient accuracy and power to be useful in astronomy.

1717 – Hadley was elected a fellow of the Royal Society.

1720 – Served the local community as governor of Barnet grammar school.

1721 – Hadley’s first Newtonian reflector had a mirror about 6 inches (15 cm) in diameter.

1726 – He built a Gregorian reflector.

1728 – He attained high office in the Society when he was elected Vice President.

1730 – Invented the reflecting octant which measured the altitude of the sun or of a star.

1731 – Hadley showed his new quadrant to theRoyal Society and published a description in his paper Description of a new instrument for taking angles which appeared in the Philosophical Transactions of the Royal Society.

1734 – Published his invention of the octant which came to be called Hadley’s quadrant.

         – He married Elizabeth Hodges who herself was wealthy.

         – Hadley published A description of a new instrument for taking the latitude or other altitude at sea.

1744 – Died on February 14th in East Barnet, Hertfordshire.