Frederick Hanley Seares

Frederick Hanley Seares


Date of Birth
May 17, 1873
Date of Death
July 20, 1964

Frederick Seares was born in Michigan and raised in Iowa and southern California. He earned his B.S. at the University of California in 1899, after which he worked as an assistant to Berkeley professor Armin O. Leuschner, from whom he learned to compute orbits and measure stellar positions. From 1899 to 1901 he continued his studies in Paris and Berlin. He taught and investigated comets and variable stars for eight years at the University of Missouri, where Harlow Shapley was his student. He published an important monograph, Practical Astronomy for Engineers in 1909. That year he joined the staff of George E. Hale’s Mt. Wilson Observatory, where he remained for 36 years. There he edited the publications of the observatory’s staff, supervised the Mt. Wilson computers (human, mostly female), and served as assistant director from 1925 until his retirement in 1940. He photographed stars in “selected areas” as part of Jacobus C. Kapteyn’s worldwide effort to determine the structure of the sidereal universe. Using photography Seares standardized the stellar magnitude system and extended it beyond the 18th magnitude. This included calibrating the magnitudes of stars near the North Pole. He used absorbing wire gauze screens and reduced apertures to compare stars of vastly different brightness. He was a pioneer in measuring and interpreting color indices of stars. He also published extensively on the brightness of the Milky Way compared to that of external galaxies and investigated interstellar absorption and reddening of starlight.

Presentation of Bruce medal

Joy, Alfred H., PASP 52, 69-79 (1940).

Some offices held

Astronomical Society of the Pacific, President, 1929.

Biographical materials

Dieke, Sally H., Dictionary of Scientific Biography 12, 264-66.
Huntington Library, Biographical Note accompanying papers
Joy, Alfred H., Biographical Memoirs of the National Academy of Science 39, 417-44
Wilds, Richard P., Biographical Encyclopedia of Astronomers, 2nd ed. (Springer, 2014), pp. 1967-68.


PASP 76, 366-67 (1964).
Redman, R.O., QJRAS 7, 75-79 (1966).
Sky & Telescope 28, 3, 123 (1964).


AIP Center for History of Physics
La Web de la Asociación Larense de Astronomía (painting)
Caltech Archives (with W. Mayer, R.C. Tolman, Einsteins)

Named after him

Lunar crater Seares
Minor Planet #11766 Fredseares


Papers, etc.

Seares's papers are at the Huntington Library. There is an excellent introduction and finding aid, presumably by Mt. Wilson archivist Helen S. Czaplicki.

Other References: Historical

Hearnshaw, J. B., The Analysis of Starlight: One Hundred and Fifty Years of Astronomical Spectroscopy (Cambridge University Press, Cambridge, UK, 1986).

Hearnshaw, J. B., The Measurement of Starlight: Two Centuries of Astronomical Photometry (Cambridge University Press, Cambridge, UK, 1996).

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Other References: Scientific

Seares, Frederick H. & A.O. Leuschner, “Elements and ephemeris of comet 1896a,” Astronomical Journal 16, 55 (1896).

Seares, Frederick H., “The Constant of Attraction,” PASP 11, 22-26 (1899).

Seares, Frederick H., “Definitive orbit of Comet 1894 IV ,” Astronomische Nachrichten 151, 81-102 (1900).

Seares, Frederick H., “Perturbations and Finding Ephemeris for Comet 1894 IV (E. Swift),” Astronomische Nachrichten 153, 125-32 (1900).

Seares, Frederick H., “Observations and Elements of Comet b 1902 (Perrine),” Laws Observatory Bulletin, University of Missouri 1, 1-6 (1902).

Seares, Frederick H., “The Polaris Vertical Circle Method of Determinig Time and Azimuth,” Laws Observatory Bulletin, University of Missouri 1, 25-84 (1906).

Seares, Frederick H., “Announcement of Preliminary Results for Variable Stars,” Laws Observatory Bulletin, University of Missouri 1, 143-64 (1907).

Seares, Frederick H., “The Art of Numerical Calculation,” Popular Astronomy 16, 349-67 (1908).

Seares, Frederick H., Practical Astronomy for Engineers (E.W. Stephens, Columbia, MO, 1909).

Seares, Frederick H., “The Algol Variable RR Draconis,” Ap.J. 36, 368-84 (1912).

Seares, Frederick H., “The Displacement Curve of the Sun’s General Magnetic Field,” Ap.J. 38, 99-125 (1913).

Seares, Frederick H., “The Photographic Magnitude Scale of the North Polar Sequence,” Ap.J. 38, 241-67 (1913).

Seares, Frederick H., “Photographic Photometry with the 60-inch Reflector of the Mount Wilson Solar Observatory,” Ap.J. 39, 307-40 (1914).

Seares, Frederick H., “The Color of the Faint Stars,” Ap.J. 39, 361-69 (1914).

Seares, Frederick H., “Relation of the Mount Wilson Photographic and Photovisual Magnitude Scales,” PASP 26, 211-13 (1914).

Seares, Frederick H., “Photographic and Photo-Visual Magnitudes of Stars Near the North Pole,” Ap.J. 41, 206-36 (1915).

Seares, Frederick H. & Harlow Shapley, “Distribution of Colors among the Stars of N. G. C. 1647 and M 67,” Proc. Nat. Acad. Sci. 1, 483-87 (1915).

Seares, Frederick H., “Color Indices in the Cluster NGC 1647,” Ap.J. 42, 120-32 (1915).

Seares, Frederick H., “Color-Photographs of Nebulae,” PASP 28, 123-26 (1916).

Seares, Frederick H., “A Simple Method for Determining the Colors of the Stars,” Proc. Nat. Acad. Sci. 2, 521-25 (1916).

Seares, Frederick H., “A Determination of the Galactic Condensation from Certain Zones of the Astrographic Catalogue,Ap.J. 46, 117-37 (1917).

Seares, Frederick H., “Preliminary Note on the Distribution of Stars With Respect to the Galactic Plane,” Proc. Nat. Acad. Sci. 3, 217-22 (1917).

Seares, Frederick H., “Further Evidence on the Concentration of the Stars toward the Galaxy,” Proc. Nat. Acad. Sci. 3, 558-62 (1917).

Hale, G.E., F.H. Seares, A. van Maanen, & F. Ellerman, “The General Magnetic Field of the Sun. Apparent Variation of Field-Strength with Level in the Solar Atmosphere,” Ap.J. 47, 206-54 (1918).

Seares, Frederick H. & Edwin P. Hubble, “The Color of the Nebulous Stars,” Ap.J. 52, 8-22 (1920).

Seares, Frederick H., “The Surface Brightness of the Galactic System as Seen from a Distant External Point and a Comparison With Spiral Nebulae,” Ap.J. 52, 162-82 (1920).

Adams, Walter S. & Frederick H. Seares, “Comparative Tests of the 100-Inch and 60-Inch Reflectors,” PASP 33, 31-34 (1921).


Seares, Frederick H., “The Masses and Densities of the Stars,” Ap.J. 55, 165-237 (1922).

Seares, Frederick H., “Revised Magnitudes for Stars Near the North Pole,” Ap.J. 56, 97 (1922).

Seares, Frederick H., “The Sun’s Motion and the Mean Parallaxes of Stars of Different Apparent Magnitudes,” Ap.J. 60, 50-59 (1924).

Seares, Frederick H., P.J. van Rhijn, Mary C. Joyner, & Myrtle L. Richmond, “Mean Distribution of Stars According to Apparent Magnitude and Galactic Latitude,” Ap.J. 62, 320-74 (1925).

Seares, Frederick H., “Some Structural Features of the Galactic System,” Ap.J. 67, 123-78 (1928).

Seares, F.H., J.C. Kapteyn, P.J. van Rhijn, M.C. Joyner, & M.L. Richmond, Mount Wilson Catalogue of Photographic Magnitudes in Selected Areas 1-139 (Carnegie Inst. of Washington Pub. No. 402, Washington, DC, 1930).

Seares, Frederick H., “Effect of Space Absorption on the Calculated Distribution of Stars,” Ap.J. 74, 91-100 (1931).

Seares, Frederick H., “A Numerical Method of Determining the Space Density of Stars,” Ap.J. 74, 268-87 (1931).

Seares, Frederick H., “Systematic Corrections to Magnitudes and an Extension of the Polar Sequence,” Ap.J. 78, 141-55 (1933).

Seares, Frederick H., The Concept of Uniformity (Carnegie institution of Washington, Washington, DC, 1938) [Elihu Root Lecture, 1938; closing section reprinted in JRASC 32, 415-416 (1938)].

Seares, Frederick H., “Photoelectric Magnitudes and the International Standards,” Ap.J. 87, 257-79 (1938).

Seares, Frederick H., “The Dust of Space,” PASP 52, 80-115 (1940).

Seares, Frederick H., Frank E. Ross, & Mary C. Joyner, Magnitures and Colors of Stars North of +80° (Carnegie Inst. of Washington Pub. No. 532, Washington, DC, 1941).

Seares, Frederick H., “The Magnitude Scale of the Bright Polar Standards,” Ap.J. 94, 21-26 (1941).

Seares, Frederick H. & Mary C. Joyner, “Some Comparisons of Spectral Classifications,” Ap.J. 98, 244-60 (1943).

Seares, Frederick H. & Mary C. Joyner, “Discussions of Color Index and Spectral Type,” Ap.J. 98, 261-301 (1943).

Seares, Frederick H. & Mary C. Joyner, “Effective Wave Lengths of Standard Magnitudes; Color Temperature and Spectral Type,” Ap.J. 98, 302-30 (1943).

Seares, Frederick H. & Mary C. Joyner, “Relation between Color Index and Effective Wave Length from the Observations of Hertzsprung and Vanderlinden,” Ap.J. 100, 264-78 (1944).

Seares, Frederick H. & Mary C. Joyner, “Revised Standards of Color Index for Polar Stars,” Ap.J. 101, 15-35 (1945).

Seares, Frederick H. & Mary C. Joyner, “Note on Departures from Black-Body Conditions in Stars,” Ap.J. 101, 36-38 (1945).

Seares, Frederick H. & Mary C. Joyner, “Photovisual Magnitudes and Color Indices in 42 Kapteyn Selected Areas,” PASP 64, 202-04 (1952).

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Other Works: Popularizations, Fiction, etc.

Seares, Frederick H., “The Brightness of the Stars—Their Distribution, Colors, and Motions,” PASP 30, 99-132 (1918) [Adolfo Stahl lecture].

Seares, Frederick H., “Counting the Stars and Some Conclusions,” PASP 40, 303-31 (1928).

Seares, Frederick H., “Form and Structure of the Galactic System,” PASP 43, 371-76 (1931).

Seares, Frederick H., “Remarks at a Dinner,” PASP 44, 371-74 (1932).

Seares, Frederick H., “Galileo,” PASP 48, 82-89 (1936).

Adams, W.S. & F.H. Seares, “The Work of the Mount Wilson Observatory,” JRASC 34, 198-205 (1940).

Seares, Frederick H., “Absorption by the Dust of Space,” Griffith Observer 5, 12, ? (Dec. 1941).