Frank was born on May 11, 1871 in New York City, New York, United States, the youngest of seven children of William Joseph and Mary (Wagner) Schlesinger. Both parents were natives of the German province of Silesia who had met and married in New York. When Frank was about nine his father died, leaving the family in financial difficulties.
Frank attended New York public schools and the College of the City of New York, where he displayed unusual mathematical ability and graduated, B. S. (Bachelor of Science) in 1890.
Later he was also enrolled as an astronomy student in the graduate school of Columbia University. He received the M. A. degree (Master of Arts) in 1897 and the Ph. D. (doctor of philosophy) in 1898. For his doctoral dissertation, using the photographic plates of star fields made by Lewis M. Rutherfurd, he measured the precise positions of stars in the Praesepe cluster.
Unable, for lack of money, to continue his studies, Schlesinger worked as a surveyor for six years. The summer of 1898 he spent at the Yerkes Observatory in Wisconsin as a voluntary assistant to the director, George Ellery Hale. For four years (1899 - 1903) he was observer-in-charge at the New International Latitude Station at Ukiah, California.
His first major astronomical contribution, which came during a two-year period (1903 - 05) on a research grant at the Yerkes Observatory, was the development of a photographic technique for measuring stellar parallax. An elegant, concise summary is the "Photographic Determination of Stellar Parallaxes" in the festschrift volume Probleme der Astronomie (1924).
In 1905 Schlesinger became director of the Allegheny Observatory at the University of Pittsburgh. He effected a reorganization of the institution and moved its instruments to a better site. He also acquired a powerful telescope designed specifically for photographic observations, the 30-inch Thaw refractor. With this, about 1914, he initiated a program that greatly increased the knowledge of parallaxes of stars in the northern celestial hemisphere. In addition, he and his colleagues carried out excellent spectroscopic work and determined the orbits of many double stars that could not be resolved visually.
Schlesinger moved to Yale in 1920 as director of its observatory, a position he held until his retirement in 1941. He at once began planning the establishment of an observing station in the southern hemisphere. He designed the instrument, a 26-inch photographic refractor of long focus, which was ground by the Brashear Company; the mechanical parts and mounting were built in the Yale workshop.
Schlesinger next took up problems of determining stellar positions and motions. Instead of depending on visual observations, as in the past, he developed a photographic method for determining the positions of stars as faint as the ninth magnitude, with the aid of a wide-angle camera designed by Frank E. Ross. These investigations, carried out with the collaboration of Ida Barney, eventually yielded precise positions and proper motions of more than 100, 000 stars, which were published in some fifteen volumes of the Transactions of the Yale Observatory.
In the 1920's and '30's Schlesinger was a striking figure at astronomical meetings, and in two lectures given during the Tercentenary Summer School of Astronomy at Harvard University (July 1936) he lucidly summarized the problems of classical astrometry, such as distortion of the photographic film, the effects of atmospheric dispersion, the sensitivity of emulsions, and optical distortion.
After five years of failing health, Schlesinger died of a heart attack at his summer home at Old Lyme, Connecticut.
Frank Schlesinger's principal contributions lay in the field of photographic astrometry - the measurement of precise star positions by photographic means. Being the acknowledged master and leader in this field, he worked out procedures to obtain the positions of the "parallax" star relative to a small number of reference stars. The methods and the results he published in a series of papers in the Astrophysical Journal (1910 - 11) and in the summary Probleme der Astronomie (1924). Other major contributions were Schlesinger's Catalogue of Bright Stars (1930) and General Catalogue of Stellar Parallaxes (1935), which became standard astronomical reference books. The crater Schlesinger on the Moon is named after him, as is the asteroid 1770 Schlesinger.
Although Schlesinger was apparently of Jewish ancestry, he had no religious affiliation.
Schlesinger was elected a member of the National Academy of Sciences (1916), the American Philosophical Society, and the American Academy of Arts and Sciences.
In his younger years Schlesinger was ambitious and single-minded in the pursuit of his work and exacting of his fellow workers. He had few interests other than astronomy. In his later years he found more time for sociability and delighted in conversation with small groups; his rich memory included stories of most of the American astronomers of his day. He was a central figure in the "Neighbors, " an informal association of Eastern astronomers that often met at Yale, and although a nonsmoker and nondrinker, he always offered his guests cigars and good wine.
On June 19, 1900, Schlesinger married Eva Hirsch. Their only child, Frank Wagner Schlesinger, later became director of the Fels Planetarium in Philadelphia and, in 1945, of the Adler Planetarium in Chicago. Schlesinger's first wife died in 1928, and on July 1, 1929, he married Mrs. Katherine Bell (Rawling) Wilcox.
