From 1930 to 1934 he was Assistant Lecturer at the University of Leeds, 1933-34 Lecturer at the University of Edinburgh and 1936-1958 Reader at King's College, University of London.
From 1948 he was a professor at Queen Mary's College, University of London and from 1952 to 1972 professor at the University of Illinois Observatory of the University of Illinois at Urbana-Champaign where he built a small astronomy department, one of the leading in the country.