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Ross, Frank Elmore

ROSS, FRANK ELMORE

(b. San Francisco, California, 2 April 1874; d. Altadena, California, 21 September 1960)

astronomy.

Ross was one of the most versatile astronomers of the twentieth century. He obtained a B.S. degree from the University of California at Berkeley in 1896 and for several years thereafter gained valuable experience through one-year appointments as teacher (mathematics and physics at Mt. Tamalpais Military Academy), on fellowships (a year each at Berkeley and Lick Observatory), and as an assistant professor of mathematics at the University of Nevada. Ross then returned to Berkeley, where he received the Ph.D. in 1901. For the next two years he computed perturbations of Watson asteroids, then spent a year as an assistant in the Nautical Almanac Office, where he attracted the attention of Simon Newcomb.

For two years Ross was research assistant at the Carnegie Institution, working on planetary and lunar problems under Newcomb. At Newcomb’s suggestion, he computed a definitive orbit of Phoebe, the ninth satellite of Saturn. This was his first major independent publication in astronomy. The differential coordinates of Phoebe given in the American Ephemeris beginning with 1909 are derived from the elements and tables published by Ross.

In 1905 Ross became director of the International Latitude Observatory at Gaithersburg, Maryland, where he took part in the observations and reductions for the precise determination of latitude required to study the motion of the earth’s axis of rotation. In 1909 the U.S. Coast and Geodetic Survey received a grant from the International Geodetic Association for the construction and operation of a photographic instrument to be used in determining the latitude variation. The instrument, known as the photographic zenith tube, or PZT, was designed by Ross.

The optical system of the PZT is patterned after the visual instrument known as the zenith tube, which had been designed by Airy and installed at Greenwich in 1851. Airy’s instrument was no longer in use, but Ross recognized the merits of its basic principle and was successful in developing an improved telescope of extremely high precision. He modified the optical system by locating the second nodal point of the lens in the focal plane, and he constructed it to operate as a photographic instrument. The PZT then had two major improvements over Airy’s instrument: the first made the PZT insensitive to tilt of the lens; the second was effective in smoothing out short-period oscillations caused by refraction and also made the instrument impersonal.

The completed instrument was installed at Gaithersburg in June 1911, and by October 1914 Ross had photographed 6,944 stars on a total of 450 nights. Thereafter the program was discontinued by the Coast and Geodetic Survey and the instrument was sold to the U.S. Naval Observatory, where it was designated as PZT no. 1 and was in continuous operation from 1915 until 1955. In 1934 the instrument was modified to determine time as well as the variation in latitude. Its use for the determination of time proved to be superior to visual methods, and copies of the instrument are used by the world’s major time services.

While at Gaithersburg, Ross completed the computations of the orbits of the sixth and seventh satellites of Jupiter that he had begun in Washington. His elements and tables were used to derive the differential coordinates of these satellites, which were published in the American Ephemeris from 1912 through 1947.

In 1912 Ross turned his attention to the cause of the discordance between the positions of Mars deduced from observations and those computed from Newcomb’s theory of Mars in Astronomical Papers; this discordance amounted to six seconds of arc in right ascension in 1905. Ross’s corrections to Newcomb’s theory, published in Astronomical Papers (1917), have been used in the American Ephemeris, beginning with the volumes for 1922.

Ross is listed in the American Ephemeris as a part time member of the staff of the Nautical Almanac Office from 1907 to 1919. In 1915 he was appointed physicist at the Eastman Kodak Company laboratories, where for nine years he studied and perfected the techniques of photography and lens design that he later successfully applied in astronomy. In 1924 he joined the staff of the Yerkes Observatory, where he continued astronomical observations until his retirement in 1939. While at Yerkes he was on the faculty of the University of Chicago as associate professor (1924–1928) and professor (1929–1939) of astronomy.

One of Ross’s early projects at Yerkes was to rephotograph the stellar fields that had been photographed by Barnard. In comparing the new plates with the older ones, he found many variable stars and stars with large proper motions. The Astronomical Journal reported these discoveries, and by 1931 Ross was credited with the discovery of 379 variable stars and 869 proper-motion stars.

Ross photographed Mars in different colors with the Mount Wilson sixty-inch reflector and with the Lick thirty-six-inch refractor at the planet’s opposition in 1926. The next year his photographic observations of Venus at Mount Wilson Observatory revealed unusual temporary markings, or shadings, in the planet’s atmosphere.

Ross spent the remainder of his life in California after his retirement from the Yerkes Observatory in 1939. He was furnished an office at the Mount Wilson Observatory, although he was not an official member of the staff. Although retired, Ross contributed to optics by designing and computing lenses. His designs included wide-angle camera lenses and elements to correct coma in the largest reflectors of his time. He is credited with the design of the twenty-inch astrograph at the Lick Observatory. Many of his lens designs were used outside astronomy.

Ross was a member of the American Astronomical Society and the National Academy of Sciences, and was an associate of the Royal Astronomical Society.

BIBLIOGRAPHY

Ross’s longer works are Latitude Observations With Photographic Zenith Tube at Gaithersburg, Md., U.S. Coast and Geodetic Survey special publication no. 27 (Washington, D.C., 1915); New Elements of Mars and Tables for Correcting the Heliocentric Positions Derived From Astronomical Papers, Vol. VI, Part IV, which is Astronomical Papers, 9 , pt. 2 (1917); and The Physics of the Developed Photographic Image (New York-Rochester, N.Y., 1924).

Articles in Astrononnische Nachrichten include “New Elements of Jupiter’s 7th Satellite,” 174 (1907), 359–362; “The Instrumental Constants of a Zenith Telescope,” 190 (1912), 19–22; “The Kimura Term in the Latitude Variation and the Constant of Aberration,” 192 (1912), 133–142; and “Magnitudes and Colors of the Eros Comparison Stars,” 239 (1930), 289–301, written with R. S. Zug.

In Astronomical Journal, Ross published “Observation of Asteroids,” 19 (1899), 194–195; “The Moon’s Mean Longitude and the Eclipse of August 21, 1914,” 28 (1914), 153–156; “The Moon’s Mean Longitude and the Eclipse of Feb. 3, 1916,” 29 (1915), 65–68; “The Sun’s Mean Longitude,” 29 , (1916), 152–156; “Investigations on the Orbit of Mars,” ibid., 157–163; “New Proper-Motion Stars,” listed in 36–41 (1925–1931) and 45–48 (1936–1939); and “New Variable Stars,” listed in 36–41 (1925–1931).

Ross’s contributions to Astrophysical Journal are “Photographic Photometry and the Purkinje Effect,” 52 (1920), 86–97; “Image Contraction and Distortion on Photographic Plates,” ibid., 98–109; “Photographic Sharpness and Resolving Power,” ibid., 201–231; “The Mutual Action of Adjacent Photographic Images,” 53 (1921), 349–374; “Astronomical Photographic Photometry and the Purkinje Effect,” 56 (1922), 345–372; “Film Distortion and Accuracy of Photographic Registration of Position,” 57 (1923), 33–48; “Mensurational Characteristics of Photographic Film,” 59 (1924), 181–191; “Characteristics of Photographic Desensitizers and Distortions on Plates due to Local Desensitizing,” 61 (1925), 337–352; “Photographs of Mars, 1926,” 64 (1926), 243249; “Photograph of the Orion Nebulosities,” 65 (1927), 137–139; “Nebulosities in Monoceros, Taurus, and Perseus,” 67 (1928), 281–295; “Photographs of Venus,” 68 (1928), 57–92; “An Abnormal Phenomenon of Photographic Plates,” 73 (1931), 54–55; “Photographs of the Milky Way in Cygnus and Cepheus,” 74 (1931), 85–90; “Correcting Lenses for Refractors,” 76 (1932), 184–201; “Astrometry With Mirrors and Lenses,” 77 (1933), 243–269; “Lens Systems for Correcting Coma of Mirrors,” 81 (1935), 156–172; “Photographic Photometry,” 84 (1936), 241–269; “Limiting Magnitudes,” 88 (1938), 548–579; “The 48-Inch Schmidt Telescope for the Astrophysical Observatory of the California Institute of Technology,” 92 (1940), 400–407; and “Parabolizing Mirrors Without a Flat,” 98 (1943), 341–346.

Popular Astronomy contains “Planetary Photography,” 31 (1923), 21; “Accuracy of Photographic Position Registration,” ibid., 22; “Distortions on Spotted Photographic Plates,” 32 (1924), 619–620; and “Photographs of Venus,” 35 (1927), 492.

Among Ross’s contributions to Publications of the Astronomical Society of the Pacific are “Lenses and Their Focal Adjustment in Relation to Photometry,” 38 (1926), 312–314; “The Optics of Reflecting Telescopes,” 46 (1934), 339–345; and “Photographic Measures of a Close Double Star,” 48 (1936), 221–222.

Other articles are “Differential Equations Belonging to a Ternary Linearoid Group,” in American Journal of Mathematics, 25 (1903), 179–205; “Semi-Definitive Elements of Jupiter’s 6th Satellite,” University of California Publications. Astronomy. Lick Observatory Bulletin, 4 (1906), 110–112; “Empirical Short Period Terms in the Moon’s Mean Longitude,” in Monthly Notices of the Royal Astronomical Society, 72 (1911), 27; “A Wide-Angle Astronomical Doublet,” in Journal of the Optical Society of America, 5 , no. 2 (Mar. 1921), 123–130; and “Limiting Magnitudes With Red Sensitive Plates,” in Publications of the American Astronomical Society, 9 (1939), 270–271.

Works of which Ross was a coauthor include Investigation of Inequalities in the Motion of the Moon Produced by the Action of the Planets, Carnegie Institution publication no. 72 (Washington, D.C., 1907), written with Simon Newcomb; Tables of Minor Planets Discovered by James C. Watson (Washington, D.C., 1910), to which A. O. Leuschner was the major contributor; Atlas of the Northern Milky Way (Chicago, 1934), written with Mary R. Calvert; and Magnitudes and Colors of Stars North of +80°, Carnegie Institution publication no. 532 (Washington, D.C., 1941), also Papers of the Mount Wilson Observatory, 6 (1941), written with F. H. Seares and M. C. Joyner.

Ralph F. Haupt

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