Margaret Walton Mayall (January 27, 1902 – December 6, 1995) was an American astronomer. She was the director of the American Association of Variable Star Observers (AAVSO) from 1949 to 1973.^[1]

Mayall (born Margaret Lyle Walton) was born in Iron Hill, Maryland, on January 27, 1902.^[1] The northern lights and Halley's comet in 1910 are stated to have stimulated her interest in astronomy at a young age.^[2] She attended the University of Delaware, where her interest in astronomy grew after taking math and chemistry courses.^[3] She then moved to Swarthmore College, where she received her Bachelor's Degree in Mathematics in 1925.^[2][4]

She earned an MA in astronomy from Radcliffe College, Harvard University, in 1928 and worked as a research assistant and astronomer at Harvard College Observatory from 1924 to 1954, initially working with Annie Jump Cannon on classifying star spectra and estimating star brightness.^[4] During this time, she would spend summers working with Margaret Hardwood of the Maria Mitchell Observatory in Nantucket, MA, where she became interested in researching variable stars.^[5] She was a research staff member at the Heat Research Laboratory, Special Weapons Group, Massachusetts Institute of Technology from 1943 to 1946.^[6]

While working in Nantucket, she met Robert Newton Mayall, a member of the American Association of Variable Star Observers (AAVSO), and would marry in 1927.^[1] They co-wrote several books on sundial and other subjects while working with the Ernst Sundial Collection of Harvard.^[5]

She died of congestive heart failure in Cambridge, Massachusetts, on 6 December 1995.^[1]

In 1957, she was the recipient of the G. Bruce Blair Gold Medal from the Western Amateur Society.^[5]

In 1958, she won the Annie J. Cannon Award in Astronomy.^[1]

In 1982, a minor planet was named, 3342 Fivesparks, in honor of her and her husband's home in Cambridge.^[5]

• Williams, Thomas R.; Saladyga, Michael (2011). Advancing Variable Star Astronomy: The Centennial History of the American Association of Variable Star Observers. Cambridge University Press. ISBN 978-1-139-49634-6.

• Letters at the AAVSO
• Oral history interview with Margaret Mayall on 11 August 1986, American Institute of Physics, Niels Bohr Library & Archives - Session I
• Oral history interview with Margaret Mayall on 12 September 1986, American Institute of Physics, Niels Bohr Library & Archives - Session II
• The Harold C. Ernst Collection of Portable Sundials