March 28, 1888 – September 20, 1968
Dinsmore Alter was an American astronomer and meteorologist. He was born in Colfax, Washington, and attended college at Westminster College in Pennsylvania. Dinsmore performed his graduate studies at the University of Pittsburgh, and earned a master's in astronomy with additional studies in the field of meteorology. In 1911 he became an instructor at the University of Alabama, teaching physics and astronomy. The following year he became an assistant professor, then an adjunct professor in 1913.
In 1914 he moved to the University of California in Berkeley, teaching astronomy while also studying for his doctorate. He gained his Ph.D. in astronomy in 1916. By 1917 he became an assistant professor of astronomy at the University of Kansas. However, when the United States entered World War I he took time off to serve as a major in the United States Army.
After returning home following the war, he rejoined the University of Kansas, and would remain at that institution for nearly 20 years. He was promoted to assistant professor in 1919, then professor in 1924.
From 1925 until 1927 he served as the vice-president of the American Meteorological Society. He was then awarded a Guggenheim Fellowship scholarship and spent two years studying astronomy in Britain. In 1935 he took a leave from the University of Kansas and became director of the Griffith Observatory. A year later he resigned his professorship to remain director at the observatory. He also served as a research associate at Caltech in Pasadena during the same period.
After the U.S. entered the Second World War, Dr. Alter took a leave from his position to serve in the armed forces for four years. He became a colonel and served in a transport division. He remained a member of the army reserve following the war, training at Fort MacArthur, Los Angeles.
His earlier studies had focused on solar observation, but after the war he became increasingly concentrated on the Moon. As his expertise increased, he became an authority on the geology of the Moon, including its surface and history. He also remained involved in astronomy research, and in 1950 he served a term as president of the Astronomical Society of the Pacific.
In 1956 he used the 60" reflector at the Mount Wilson Observatory to observe a peculiar obscuration on part of the floor of Alphonsus crater, which brought him worldwide notice. This is a class of events now called a transient lunar phenomenon.
During 1958 he reached mandatory retirement age, and was officially retired on March 31. However he remained active during his retirement, writing several books on astronomy and performing consulting services. He also served as Director Emeritus for the Griffith Observatory.
The Lunar crater Alter is named in his honor.