Alfred H. Joy (1882–1973) was an astronomer at the Mount Wilson Observatory from 1915 to 1973 who measured spectroscopic parallaxes and radial velocities of stars and studied variable stars. He invented the T Tauri classification.

After graduating MA from Oberlin College in 1904, Joy went on to work at the American University of Beirut in the Syrian Protestant College as a professor of astronomy and the director of the observatory. He was forced to return to the U.S. in 1915 because of the 1st World War.

Ejnar Hertzsprung (8 October 1873 – 21 October 1967) was a Danish chemist and astronomer.

Hertzsprung was born in Copenhagen. In the period 1911–1913, together with Henry Norris Russell, he developed the Hertzsprung–Russell diagram.

Wilhelmina Iwanowska was born in Wilno, Poland, where she studied mathematics at the University, obtaining her D.Sc. degree in astronomy in 1933 and a Docent in 1937. She had been working at the Wilno Observatory, however, since 1927.

Helen Battles Sawyer Hogg, CC (1 August 1905 – 28 January 1993) was an astronomer noted for her research into globular clusters. She is best remembered for her astronomy column, which ran from 1951 until 1981 in the Toronto Star, and her articles on the history of astronomy which ran from 1946 until 1965 in the Journal of the Royal Astronomical Society of Canada under the title “Out of Old Books”.

Leo Goldberg (26 January 1913 – 1 November 1987) was an American astronomer who held professorships at Harvard and the University of Michigan and the directorships of several major observatories. He was president of both the International Astronomical Union and the American Astronomical Society. His research focused on solar physics and the application of atomic physics to astronomy, and he led many of the early efforts to study the Sun from space telescopes.

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Gerald Maurice Clemence (16 August 1908 — 22 November 1974) was an American astronomer. Inspired by the life and work of Simon Newcomb, his career paralleled the huge advances in astronomy brought about by the advent of the electronic computer. Clemence did much to revive the prestige of the U.S. Nautical Almanac Office.

Robert Hanbury Brown, AC FRS (31 August 1916 – 16 January 2002) was a British astronomer and physicist born in Aruvankadu, India. He made notable contributions to the development of radar and he later conducted pioneering work in the field of radio astronomy. He was rumoured to have been the original radar scientist who inspired the term boffin during World War II.

Ira Sprague Bowen (December 21, 1898 – February 6, 1973) was an American astronomer. In 1927 he discovered that nebulium was not really a chemical element but instead doubly ionized oxygen. In 1946 he was made director of Mount Wilson Observatory upon the retirement of Walter Sydney Adams.

Dr. Bowen was made an honorary member of the Royal Astronomical Society of Canada on 1956-02-17.

Frank Maine Bateson (d. 2006), director of the Variable Star section of the Royal Astronomical Society of New Zealand since 1928.

Bart Jan Bok (Hoorn, 28 April 1906 – Tucson, 5 August 1983) was a Dutch-American astronomer.

He was born in the Netherlands, but spent a good deal of his childhood days growing up in what was then known as the Dutch East Indies. He was educated at the Leiden and Groningen Universities. In 1929 he married fellow astronomer Dr. Priscilla Fairfield Bok, and for the remainder of their lives the two collaborated closely on their astronomical work. They had two children, Joyce and John.