William Gascoigne (scientist)

William Gascoigne (1612 to 1644) was an English astronomer, mathematician and maker of scientific instruments from Middleton, Leeds, who invented the micrometer and the telescopic sight. He belonged to a group of astronomers in the north of England who followed the astronomy of Johannes Kepler, which included Jeremiah Horrocks and William Crabtree. In the late 1630s a thread of spider web caught at the shared focus of the two lenses of a Keplerian telescope, and he saw it sharp within the field of view. He realised that crossed wires at the focus would let him point the telescope accurately, and so invented the telescopic sight. He added it to a five foot sextant modelled on that of Tycho Brahe and measured angles between heavenly bodies far more accurately than before. By introducing two points whose separation could be adjusted with a screw of known pitch, he could size the Moon and planets, the principle of the micrometer. He met William Crabtree around 1640, who saw the importance of these inventions at once. He claimed an Oxford education, though no record of it has been found, and he died in 1644.