He became the ninth Astronomer Royal in 1910. His main concern was with the accurate measurement of star positions and proper motions, which revealed the distribution of stars in our part of the Galaxy. From observations at several eclipses he identified elements in the solar chromosphere from lines in its spectrum; this success motivated the Greenwich eclipse expedition of 1919 which confirmed Einstein’s prediction that a gravitational field bends starlight. Dyson introduced the broadcasting of radio time signals from Greenwich in the 1920s.