Ryle M Smith F G Elsmore B A Preliminary Survey of the Radio Stars in the Northern Hemisphere MNRAS 110 508 523 1950 Smith F Graham 1923 Astronomer who joined Martin Ryle s radio group in 1946 He observed Cygnus A using a Michelson interferometer Eric Weisstein s World of Physics at 80 MHz He also built the Long Michelson Interferometer at the Old Rifle Range in Cambridge in 1950 This device operated at a wavelength of 3 7 meter and was operated using Ryle s phase switching technique to compile the 1C survey in 1950 He also used the interferometer to measure the electron Eric Weisstein s World of Physics density in the ionosphere Eric Weisstein s World of Astronomy c f Evans In 1977 his book Pulsars was published Sullivan 1984 p 413 I have updated the 1C page accordingly