William Gascoigne ( scientist ) William Gascoigne ( 1612 – 2 July 1644 ) was an English astronomer , mathematician and maker of scientific instrument s from Middleton , Leeds who invented the micrometer . He was one of " nos Keplari " a group of astronomers in the north of England who followed the astronomy of Johannes Kepler which included , Jeremiah Horrocks and William Crabtree . Life and work . Gascoigne was born in Middleton , Leeds in 1612 , the son of a minor country gentleman . His father was Henry Gascoigne , Esq . , of Thorpe - on - the - Hill in the parish of Rothwell , near Leeds , Yorkshire . His mother was Margaret Jane , daughter of William Cartwright . Little is known of his early life . He claimed he was educated at the University of Oxford , although no record of this has been found . In the late 1630s , Gascoigne , was working on a Keplerian optical arrangement when a thread from a spider ’ s web happened to become caught at exactly the combined optical focal points of the two lenses . When he looked through the arrangement Gascoigne saw the web bright and sharp within the field of view . He realized that he could more accurately point the telescope using the line as a guide , and went on to invent the telescopic sight by placing crossed wires at the focal point to define the centre of the field of view . He then added this arrangement to a sextant modelled on the instrument used by Tycho Brahe , although Tycho ’ s sextant was only a naked - eye instrument . Gascoigne ' s sextant was five feet in radius , and measured the distance between astronomical bodies to an unprecedented degree of accuracy . Gascoigne then realised that by introducing two points , whose separation could be adjusted using a screw , he could measure the size of the image enclosed by them . Using the known pitch of the screw , and knowing the focal length of the lens producing the image , he could work out the size of the object , such as the Moon or the planets , to a hitherto unattainable degree of accuracy . Gascoigne met the Lancashire astronomer William Crabtree , probably in 1640 . After making observations at Gascoigne ' s home , Crabtree was much taken with these inventions and immediately saw their significance . On his return to his home in Broughton , just outside Manchester , he wrote to Gascoigne asking if he might obtain such instruments and also wrote to his friend Jeremiah Horrocks about them . He wrote again to Gascoigne on 28 December 1640 saying , My friend Mr . Horrox professeth that little touch which I gave him hath ravished his mind quite from itself and left him in an Exstasie between Admiration and Amazement . I beseech you Sir , slack not your Intentions for the Perfection of your begun Wonders . This invention was later taken up and improved by the scientist and astronomer Richard Towneley who was the nephew of Gascoigne ' s friend Christopher Towneley . Towneley later brought the instrument to the attention of Robert Hooke , who used it to calculate the size of comets and other celestial bodies . The micrometer , as it became known , was to lie at the heart of astronomical measurement down to the twentieth century . In 1642 , civil war broke out in England , and Gascoigne received a commission as Providore for Yorkshire in the army of King Charles I . Crabtree lived in Broughton , just outside Manchester which was on the parliamentary side and all correspondence between the two ceased . Gascoigne died at the Battle of Marston Moor , Yorkshire , on 2 July 1644 as did Charles Towneley , the father of his friend Richard Towneley . After Gascoigne ' s death some of his papers and fragments of correspondence between Crabtree and Gascoigne came into the possession of Christopher and Richard Towneley . They brought them to the attention of John Flamsteed , the first Astronomer Royal , who came to see Horrocks , Crabtree , and Gascoigne as the founding fathers of British research astronomy and the intellectual heirs of Galileo and Kepler . He began his massive three - folio volume " Historia Coelestis Britannica " ( 1725 ) by printing five pages of their surviving letters and observations , made between 1638 and 1643 . Many of Gascoigne ' s papers and correspondence were lost during the English Civil War and later in the Great Fire of London , but most of what is known to remain is kept in the Bodleian Library at the University of Oxford .