David Peck Todd (Peck was his mother's maiden name), United States astronomer, obtained the degrees Bachelor of Arts (AB, 1875) and Master of Arts (AM, 1878) at Amherst College, Massachusetts. While still an undergraduate student he made observations of the satelites of Jupiter and the transit of Venus on 9 December 1874. After graduating in 1875 he joined the United States Naval Obsevatory, directed by Simon Newcomb*. The next year his first important work was published: A continuation of De Damoiseau's tables of the satelites of Jupiter to the year 1900. It was printed for the American Ephemeris and Nautical Almanac in 1876 and became a standard work of reference. In 1878 he led the observatory's expedition to Dallas, Texas, to observe a total eclipse of the sun. It was the first of many such expeditions, which meant that much of his career was devoted to the study of solar eclipses. Upon his return he worked as an assistant in the office of the American Ephemeris and Nautical Almanac, but resigned in 1881 to take up an appointment as associate professor (from 1892 professor) of astronomy and director of the observatory at Amherst College, a post he held until his retirement in 1920. During 1882-1887 he was also professor of astronomy and higher mathematics at Smith College, an educational institution for women in nearby Northampton, Massachusetts. He erected new astronomical observatories at both Smith College (1886-1887) and Amherst College (1903-1905). In 1879 he married Mabel Loomis, the daughter of an astronomer, who collaborated with him in much of his work.
Todd's early papers dealt with the phenomena of Jupiter's satalites (1875, 1877), occultations of Saturn and Uranus (1877), his observations of the transit of Mercury on 6 May 1878 (1879), and the solar parallax (1880, 1883). In 1882 he was placed in charge of observations of the transit of Venus at Lick Observatory, California, publishing an account of the work in the American Journal of Science (1883). In 1887 he led an expedition to observe a total solar eclipse in Japan and the next year published American eclipse expedition to Japan, 1887: Preliminary report.... While in Japan he developed a method and apparatus for the automatic photography of the solar corona during an eclipse, using multiple telescopes. After further improvements he described the procedure in "Automatic photography of the corona" in the Astrophysical Journal (1897).
His next venture was to lead the United States Scientific Expedition to West Africa in USS Pensacola during 1889-1890. One of the objects of the expedition was for Todd and H. Jacoby* to observe the total solar eclipse of 22 December 1889, but the event was clouded out. The expedition members also made meteorological observations (Professor C. Abbe*), and observations of the earth's gravity and magnetic field (E.D. Preston*). Measurements were made at 14 stations, most on islands in the North and South Atlantic, but including five on the West African coast. One of the latter was the Royal Observatory, Cape of Good Hope, where they arrived on 18 January 1890 to make a complete series of pendulum and magnetic observations and conduct various meteorological investigations. The staff of the observatory was given every opportunity to examine, and in some cases to test, the expedition's fine collection of instruments. Todd described the expedition's progress in Nature in 1890 and 1891.
In later years Todd led Amherst eclipse expeditions to Japan (again, 1896), Tripoli (1900), the Dutch East Indies (1901), Tripoli again (1905), Russia (1914), Florida (1918), and Brazil (1919). In 1907 he was furthermore in charge of the Percival Lowell Mars Expedition to the Andes Mountains, where he made over 12 000 photos of Mars that were used to revise the map of the planet. His hobby was aircraft design and aviation, and in 1925 he made the first photo of the solar corona from an aircraft. In 1932 he observed his last total solar eclipse, in New England. He was a Fellow of the American Association for the Advancement of Science, the Astronomical Society of America, and the Washington Philosophical Society. In addition to numerous papers on eclipse observations and planetary astronomy he published a textbook, A new astronomy (1897, plus 24 later editions in English and translations into Hungarian, Turkish and Chinese), as well as several more popular books: Stars and telescopes; a handbook of popular astronomy (1899), Astronomy; the science of heavenly bodies (1922), Astronomy today (1924), and The story of the starry universe (1930). In 1888 he was awarded an honorary PhD degree by Washington and Jefferson College.