The Royal Greenwich Observatory

The Royal Observatory was established by King Charles II in the year 1675 for the specific practical purpose of ‘rectifying the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so-much-desired longitude of places for the perfecting the art of navigation’. At that time the most accurate star catalogue available was the catalogue of 1000 stars, prepared by Tycho Brahe about 1598; only 777 of the stars had been properly observed, and the star places, whose average errors were of the order of T to 2', were not sufficiently accurate for the purpose of determining longitudes. The best tables for giving the position of the Moon were liable to errors as great as 20'. Flamsteed, who was appointed the first Astronomer Royal, realized that a good stock of observations, continued for many years, was needed in order to provide star places with all the accuracy that was attainable and to furnish positions of the Sun, Moon and planets which could serve as the basis for the construction of satisfactory tables of their motions. So, from its very foundation, the Observatory started upon systematic and long-continued programmes of observation which, throughout its history, have formed its most significant and important contribution to astronomy.