Night work at Greenwich Observatory, London, 1880.
© Science Museum / Science & Society Picture Library
Plate taken from Illustrated London News (Vol 80/2 p 565). The observatory had enjoyed increasing prominence following its reorganisation by Sir George Bidell Airy (1801-1892), Greenwich Mean Time (GMT) becaming the official time in Britain 1880. Advances in telescopes over the century allowed large instruments to be used with considerable accuracy. William Lasell (1799–1880), designed and built the first equatorially-mounted big reflecting telescopes, and Grubb telescopes used large-diameter bearings for good stability and an equatorial driving clock, powered by a falling weight and controlled by a centrifugal governor.