American astronomer stubs

Olin Chaddock Wilson (January 13, 1909 – July 13, 1994) was an American astronomer best known for his work as a stellar spectroscopist.Born in San Francisco, California as the son of a lawyer, Wilson showed an interest in physics at an early age. He studied astronomy and physics at the University of California, Berkeley and wrote his first scientific paper in 1932 on the subject of the speed of light. He received his PhD from the California Institute of Technology in 1934.
Wilson was a staff member of Mount Wilson Observatory (not named after Olin Wilson) for most of his research career where he studied stellar chromospheres. He was the first scientist to discover activity cycles, similar to the solar 11-year sunspot cycle, in other stars. In collaboration with Vainu Bappu, an Indian astronomer, he also showed that there was a correlation between the width of the Ca II lines in stellar spectra and the star's luminosity, the Wilson–Bappu effect.He gave the Henry Norris Russell Lectureship in 1977 and won the Bruce Medal in 1984.

Robert Paul Kraft (June 16, 1927 – May 26, 2015) was an American astronomer. He performed pioneering work on Cepheid variables, stellar rotation, novae, and the chemical evolution of the Milky Way. His name is also associated with the Kraft break: the abrupt change in the average rotation rate of main sequence stars around spectral type F8.

Harold Lester Johnson (April 17, 1921 – April 2, 1980) was an American astronomer.
Harold Johnson was born in Denver, Colorado, on April 17, 1921. He received his early education in Denver public schools and went to the University of Denver, graduating with a degree in mathematics in 1942. Johnson was recruited by the MIT Radiation Laboratory to work on World War II related radar research. After the war Johnson began graduate studies in astronomy at University of California, Berkeley where he completed his thesis under Harold Weaver in 1948.
In the following years working at Lowell Observatory, University of Wisconsin–Madison, Yerkes Observatory (where he met William Wilson Morgan), McDonald Observatory, University of Texas–Austin, the Lunar and Planetary Laboratory in Tucson, Arizona, and the National Autonomous University of Mexico he applied his instrumental and electronic talents to developing and calibrating astronomical photoelectric detectors.
He died of a heart attack in Mexico City in 1980. He and his wife, Mary Elizabeth Jones, had two children.
Johnson was awarded the Helen B. Warner Prize by the American Astronomical Society in 1956. He was elected to the National Academy of Sciences in 1969. He is remembered for introducing the UBV photometric system (also called the Johnson or Johnson-Morgan system), along with William Wilson Morgan in 1953.