Harold Delos Babcock

Harold Delos Babcock


Date of Birth
January 24, 1882
Date of Death
April 8, 1968

Born in Wisconsin, Harold Babcock finished high school in Los Angeles and earned his bachelor’s degree in electrical engineering at the University of California in 1906. In 1909 he became one of the first staff members of the Mt. Wilson Observatory, where he remained until retirement in 1948, after which he continued research and instrument-building. In the early years he made precision measurements of spectra in the laboratory and participated in solar research with George E. Hale. Babcock’s precise laboratory studies of atomic spectra allowed others to identify the first “forbidden” lines in the laboratory and to discover the rare isotopes of oxygen. With C.E. St. John he greatly improved the precision of the wavelengths of some 22,000 lines in the solar spectrum, referring them to newly-determined standards, and extending measurements into the ultraviolet and infrared. With his son, Horace W. Babcock, he measured the distribution of magnetic fields over the solar surface to unprecedented precision. He supervised the construction of a ruling engine and ruled excellent large gratings, including those used in the coudé spectrographs of the 100 and 200-inch telescopes.

Presentation of Bruce medal

Kron, Gerald E., PASP 65, 65-69 (1953).

Some offices held

Astronomical Society of the Pacific, President, 1937.

Biographical materials

Bowen, Ira S., Biographical Memoirs of the National Academy of Science 45, 1-19 (1975).


Joy, A.H., Sky & Telescope 35, 350 (1968).
Plaskett, H.H., QJRAS 10, 68-72 (1969).


AIP Center for History of Physics
Huntington LIbrary

Named after him

Lunar crater Babcock
Minor Planet #3167 Babcock (with H.W. Babcock)


Papers, etc.

Some of Babcock’s papers are at the Huntington Library. The AIP Niels Bohr Library & Archives has a 1962 Manuscript Autobiography (38 pp.), as well as 1975 and 1977 oral history interviews of Horace Babcock and others who worked with Harold Babcock.

Other References: Historical

Search ADS for works about Babcock

Adams, Walter S., “Early Solar Research at Mt. Wilson,” Vistas in Astronomy 1, 619-623 (1955).

Babcock, Harold D., “George Ellery Hale,” PASP 50, 156-65 (1938).

Babcock, Harold D., “In 1903,” PASP 51, 19-23 (1939) [poem recounting first visit to Mt. Wilson].

Babcock, Horace W., “Diffraction Gratings at the Mount Wilson Observatory,” Physics Today 39, 7, 34-42 (1986).

Howard, Robert, “Eight Decades of Solar Research at Mt. Wilson,” Solar Physics 100, 1-2, 171-187 (1985).

Hufbauer, Karl, Exploring the Sun: Solar Science Since Galileo (Johns Hopkins Univ. Press, Baltimore, 1991).

Sandage, Allan, Centennial History of the Carnegie Institution of Washington. Vol. 1, The Mount Wilson Observatory: Breaking the Code of Cosmic Evolution (Cambridge Univ. Press, Cambridge, UK, 2004).

Simmons, Michael, “The History of Mount Wilson Observatory: Bringing Astronomy to an Isolated Mountaintop,” (Mt. Wilson Observatory Association, 1983).

Other References: Scientific

Search ADS for works by Babcock

Babcock, Harold D., “The Zeeman effect for Chromium,” Ap.J. 34, 217-33 (1911).

St. John, Charles E. & Harold D. Babcock, “Wave-Lengths of Lines in the Iron Arc from Grating and Interferometer Measures λ 3370 – λ 6750,” Ap.J. 53, 260-99 (1921).

Babcock, Harold D., “A Study of the Infra-Red Solar Spectrum with the Interferometer,” Ap.J. 65, 140-62 (1927).

Babcock, Harold D., “A Photographic Study Of the Solar Spectrum in the Region λ10000 to λ11000 A,” PASP 41, 274-76 (1929).

Babcock, Harold D., “The Construction and Characteristics of Some Diffraction Gratings,” PASP 45, 283-88 (1933).

Russell, Henry Norris, Harold D. Babcock, & Charlotte E. Moore, “Series Lines of Magnesium in the Solar Spectrum,” Phys. Rev. 46, 826-27 (1934).

Babcock, Harold D., Charlotte E. Moore, & Wendell P. Hoge, “A Scale of Wave-Lengths in the Infra-Red Solar Spectrum,” Ap.J. 83, 103-20 (1936).

Babcock, Harold D., “Chemical Compounds in the Sun.,” Ap J. 102, 154-67 (1945).

Babcock, Harold Delos & Charlotte E. Moore, “The Solar Spectrum λ2914–λ3060,” Astronomical Journal 52, 41 (1946).

Babcock, Harold D., Charlotte E. Moore, & Mary F. Coffeen, “The Ultraviolet Solar Spectrum, λλ2935 to 3060,” Ap.J. 107, 287-302A (1948) [Errata].

Babcock, Harold D. & Horace W. Babcock, “The Ruling of Diffraction Gratings at the Mount Wilson Observatory,” Astronomical Journal 56, 120 (1951).

Babcock, Horace W. & Harold D. Babcock, “Mapping the Magnetic Fields of the Sun,” PASP 64, 282-87 (1952).

Babcock, H.W. & H.D. Babcock, “Photospheric Magnetic Fields,” in Electromagnetic Phenomena in Cosmical Physics, Proceedings from IAU Symposium no. 6. Edited by B. Lehnert. International Astronomical Union. Symposium no. 6, (Cambridge University Press, 1958), pp. 239-47.

Babcock, Harold D., “The Sun’s Polar Magnetic Field,” Ap.J. 130, 364-65 (1959).

Other Works: Popularizations, History, etc.

Babcock, Harold D., “Astronomy without a Telescope,” Popular Astronomy 43, 81-92 (1935).

Babcock, Harold D., “What’s in the Air?” Astronomical Society of the Pacific Leaflets 6, 322-29 (1953) [Leaflet #291, the address given on receipt of the Bruce Medal].