Sir Frank Watson Dyson (1868-1939) was born at Measham, near Ashby-de-la Zouch, on 8 January 1868, the eldest of the four sons and three daughters of the Revd Watson Dyson, a Baptist minister, and his wife Frances (née Dodwell). He spent most of his childhood in Halifax, and was educated at Bradford Grammar School. He joined Trinity College, Cambridge, in 1886, where he was second wrangler in the mathematical tripos in 1899, and first Smith's Prizeman in 1891. He became Fellow of Trinity in 1891, and the following year was awarded the Sheepshanks Scholarship and the Isaac Newton Studentship for research in astronomy. He chose to specialise in the theory of potential, and published his first paper on 'The Potential of Ellipsoids of Variable Densities'. He won acclaim for his work on 'The Potential of an Anchor Ring', which was published in 'Philosophical Transactions' in 1893, and the following year was appointed Chief Assistant at the Royal Observatory, Greenwich. Later in 1894 he married Caroline (Carrie) Bisset Best (d. 1937), with whom he went on to have two sons and six daughters.

Dyson's first major task at Greenwich was to supervise the Observatory's share of the international cooperative scheme for the preparation of a star catalogue and star map of the whole sky - the 'Carte du Ciel'. His work on this subject convinced him of the need for further knowledge of the motion of the stars. As a result, he undertook, with William Grasset Thackeray, a new reduction of the 27,000 observations of more than 4,000 circumpolar stars made by Stephen Groombridge at Blackheath between 1806 and 1819. He was appointed Astronomer Royal for Scotland in 1906, and proceeded to investigate stellar motions in relation to the distance and luminosities of the stars and to their distribution. He was also successful in his attempt to confirm that the phenomenon of star streaming, first shown on 1904 by Jacobus Cornelius Kapteyn, applied equally to stars of large proper motion.

Following the retirement of W.H.M. Christie in 1910, Dyson left Edinburgh to take up the post of Astronomer Royal at Greenwich. His work thereafter was closely linked to that of the Royal Observatory. He extended the functions of the Observatory in many directions, including the determination of stellar magnitudes, effective wavelengths and temperature. He placed importance on the reduction and discussion of meridian observations, with these programmes being chosen especially to meet the needs of practical astronomy. Prior to the First World War he helped to extend and improve the work on magnetic observations. After the war, when electric railways were built close to the Royal Observatory, he negotiated with the railway companies responsible and persuaded them to pay for the transfer of magnetic work to Abinger. He presided over the construction of a new transit circle, which was built to the highest modern standards, and also oversaw the installation of a 36-inch telescope, which was given by W. Johnston Yapp in commemoration of Dyson's work as Astronomer Royal.

Dyson was instrumental in introducing improvements to the Greenwich Time Service. He installed the new free-pendulum clocks as the standards of time, which provided much greater accuracy than their predecessors. As a result of the modernisation, he was able to introduce the 'Six Pips'. The time signal, relayed from Greenwich via the British Broadcasting Corporation, was inaugurated in 1924, and this was augmented in 1927 by the worldwide wireless signal system for shipping, which transmitted from Rugby in Warwickshire.

Another of Dyson's long-standing interests was the solar eclipse. He observed the total eclipses of 1900 (Portugal), 1901 (Sumatra), 1905 (Tunis), 1912 (Paris), 1927 (Gigglewick) and 1932 (U.S.A.), and through this contributed much to the knowledge of the spectra of the Sun's atmosphere and corona. His most significant contribution in this field related to the eclipse of 1919. He recognised that the Sun's central position in relation to the Hyades at the time of this eclipse would afford an unusually good opportunity to test Albert Einstein's prediction of the deflection of starlight in the Sun's gravitational field. With this in mind, he organised two expeditions to study the eclipse - one from Greenwich to Sobral in Brazil, and one from Cambridge, under Sir Arthur Eddington, to Principe in West Africa. The successful results of these expeditions confirmed the prediction and did much to secure general acceptance of Einstein's generalised theory of relativity.

Dyson was at the forefront of the attempt to reconstruct international goodwill and cooperation following the conclusion of the First World War. He was heavily involved in the International Research Council and the formation of the International Astronomical Union, of which he was the President between 1928-1932. He held many other important posts, serving as President of the Royal Astronomical Society between 1911 and 1913, and of the British Astronomical Association, 1916-1918. He was elected a Fellow of the Royal Society in 1901, and was Vice-President, 1913-1914. He was knighted in 1915, and received the K.B.E. in 1926. In 1921 he was awarded a Royal Medal by the Royal Society in 1921 for his investigations of the distribution and movements of stars and the relationship of these to the structure of the Galaxy. He was also selected for the Bruce Medal of Astronomical Society of the Pacific (1922) and the Gold Medal of the Royal Astronomical Society (1925). For many years he was the president of the British Horological Institute, which awarded him their Gold Medal in 1928. He was also twice Master of the Worshipful Company of Clockmakers, and the holder of honorary degrees from the universities of Oxford, Cambridge, Edinburgh, Durham, Leeds, Toronto, Perth and Melbourne.

Dyson produced many publications, a large proportion of which were joint efforts with members of his staff and other scientists. Some of the most notable of his works include 'Determination of Wave Length from Spectra Obtained at the Total Eclipse of 1900, 1901 and 1905' (1906); 'Astronomy' (1910); 'Observations of Stellar Parallax from Photographs' (1925); and 'Eclipses of the Sun and Moon' (1937), with Richard van der Riet Woolley. He also published research papers on the distribution and movement of stellar universe.

Dyson retired as Astronomer Royal in 1933, and spent much of the remainder of his life organising and supervising the removal of the Radcliffe Observatory to Pretoria in South Africa. He died on 25 May 1939 during the homeward voyage from Australia, where he had been visiting one of his daughters, and was buried at sea.