an English mathematician, and laid claim to the invention of the octant, two years after Thomas Godfrey claimed the same. Hadley also developed ways to make precision aspheric and parabolic objective mirrors for reflecting telescopes. In 1721 he showed the first parabolic Newtonian telescope to the Royal Society. This Newtonian, with a 6-inch-diameter (150 mm) primary mirror, compared favorably with the large aerial refracting telescopes of the day. He also made Gregorian telescopes with accurately shaped mirrors.
