Adrien Auzout

Adrien Auzout, who lived from 1622 to 1691, was a French astronomer born in Rouen, the eldest child of a clerk in the court of Rouen. He left for Paris in the 1640s, where he became well known in academic circles, and in 1664 and 1665 he observed comets and argued that they follow elliptical or parabolic orbits, in this opposed by his rival Johannes Hevelius. He was briefly a member of the Académie Royale des Sciences from 1666 to 1668, a founding member of the Paris Observatory and, in 1666, a Fellow of the Royal Society of London. Described as a good optician and maker of telescopes, he perfected the use of the micrometer, in 1647 performed an experiment that showed the role of air pressure in the mercury barometer, and in 1667 and 1668 worked with Jean Picard to attach a telescopic sight to a 38-inch quadrant and so determine positions on the Earth accurately. He spent his last twenty years in Italy and died in Rome, and a lunar crater is named after him.