John Flamsteed FRS, Astronomer Royal John Flamsteed was an English astronomer who is best known for his excellent stellar observations; his appointment by King Charles II, in 1675, as the first Astronomer Royal; and his founding of the Royal Observatory at Greenwich the following year, 1676. Flamsteed was also a member of the Royal Society.[1] In the early 1670s, Flamsteed published a set of equation tables for converting Solar Time to Mean Time to Local Mean Time. As all clocks still had to be set locally by using a sundial, Flamsteed’s Equation of Time tables (as they were called) were indispensable and represent his most obvious contribution to horological development. Like most astronomers of his day, Flamsteed believed that the solution to the longitude problem would be an astronomical one rather than a horological one – most likely achieved by measuring the position of the navigator relative to celestial bodies such as Jupiter’s moons, which had been discovered by Galileo Galilei in 1610.[2] This belief was shared by King Charles II who wanted to beat the French to a solution and, as quoted by Sobel, duly tasked his new Astronomer Royal to rectify Tables of the Motions of the Heavens, and the Places of fixed Stars, so as to find out the much-desired Longitude at Sea, for perfecting the art of Navigation.[3] Within six months of appointing Flamsteed, on 22 June 1675, Charles issued a warrant to initiate construction of a royal observatory. His proclamation read: Whereas, in order to the finding out of the longitude of places for perfecting navigation and astronomy, we have resolved to build a small observatory within our park at Greenwich, upon the highest ground, at or near the place where the castle stood, with lodging-rooms for our astronomical observator and assistant. With Sir Jonas Moore, Flamsteed planned the construction of a new observatory on the hill above the abandoned royal rebuilding project of Greenwich Palace. The Royal Observatory was duly completed within a year of his appointment. Beyond his salary, there was no spare cash for equipment, so he was forced to borrow Robert Hooke’s quadrant, and apparently two clocks were commissioned (at Sir Jonas Moore’s expense) from the master clockmaker Thomas Tompion. Each clock was reportedly equipped with thirteen foot pendulums that ‘make each single vibration in two seconds of time; and their weights need only to be drawn up once…’.[4] During his tenure as Astronomer Royal, Flamsteed met Edmund Halley at Oxford. The two began working together, and Halley aided Flamsteed in compiling an accurate catalogue of northern stars. As there was desperate need by astronomers for such a catalogue, Isaac Newton, by way of the Royal Society, put enormous pressure upon Flamsteed to publish.[5] However, reticent to make his incomplete observations public, Flamsteed kept his recordings under lock and key at Greenwich. Somehow, Newton and Halley managed to get hold of most of Flamsteed’s data. Halley then edited the incomplete observations, and he and Newton published their own pirated edition of Flamsteed’s star catalogue. A total of 400 copies were printed in 1712. Enraged, Flamsteed managed to collect and burn 300 of these.[6] Flamsteed devoted over 40 years to mapping the heavens, conducting and meticulously recording some 30,000 observations.[7] It was not until 1725 that his completed star catalogue, Historia Coelestis Britannica, was published posthumously. At the time, it was more accurate than any previous work. It listed around 3000 stars with their positions and tripled the number of entries in Danish astronomer Tycho Brahe’s sky atlas. This was undoubtedly Flamsteed’s greatest contribution to his field. John Flamsteed died on 31 December 1719. End Notes [1] Birks 1999. [2] Wooten 2010, 124 [3] Sobel 2007, 31, also see 53. [4] Carter 2021, 102. [5] Clark et al. 2001. [6] Sobel 2007, 59-60. [7] Sobel 2007, 92. References Birks, John L. 1999. John Flamsteed: The first Astronomer Royal at Greenwich. London: Avon Books. Carter, J. 2021. The John C Taylor Collection: Part I (Selling Exhibition Catalogue, Carter Marsh & Co.). Winchester: Carter Marsh & Co. Clark, S. P. and D. H. Clark. 2001. Newton’s Tyranny: The supressed scientific discoveries of Stephen Gray and John Flamsteed. New York, NY: W.H. Freeman & Company. Flamsteed, J. 1725. Historia Coelestis Britannica: Tribus voluminibus contenta. London: Meere. Sobel, D. 2007. Longitude: The story of a lone genius who solved the greatest scientific problem of his time. London: Harper Perrennial. Wooten, D. 2010. Galileo: Watcher of the skies. New Haven: Yale University Press. Further Reading Royal Museums Greenwich. ‘The Astronomer Royal’. https://www.rmg.co.uk/stories/topics/astronomer-royal. Image Credit John Flamsteed. Mezzotint, later than 1726, after Sir G. Kneller, 1702. Wellcome Collection. Public Domain Mark
