MWO founder George Ellery Hale atop Mt. Wilson, 1904 Huntington Library


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Mount Wilson Observatory is operated by the Mount Wilson Institute under an agreement with the Carnegie Institution of Washington. The Observatory occupies lands belonging to the USDA Forest Service set aside under a long-term leasehold agreement between CIW and the USDA Forest Service. The Observatory subscribes to the USDA non-discrimination policy as expressed here.

Banner photographs by David Jurasevich

Mount Wilson's First Century
On December 20, 2004, Mount Wilson Observatory celebrated the Centennial of its founding. Presented here a partial list of the significant events and achievements that marked the first century of this historic observatory.

The highlighted links in the timeline and other pages offer related information and pictures from both the Mount Wilson and other historical archives and current web sites. Links to sites external to Mount Wilson will open in a separate browser window.

"As one who has had the extremely good fortune to have been associated with the Mount Wilson Observatory for much of its one hundred-year existence, I have vivid memories of its early years. I remember not so much the steel and glass Observatory, but its people. History has bestowed a nearly iconic status on this remarkable group, but they were, after all, real human beings. These were people with character strengths and faults, people with families, people with dedication to their profession yet with a keen interest in the community and the environment in which they worked. They enjoyed many of the same things that most of us do today. Often they were not too busy to have a game of tennis with a callow youth they knew as the son of one of their members. My regret, of course, is that I did not have the maturity at the time to engage them in discussions of cosmology and astrophysics. If I had, however, it is very unlikely that they would have played tennis with me.

On this occasion marking the centennial of the Observatory I do look back on that fabulous era. Even more, however, I look forward to the next one hundred years. Years that will see Mount Wilson continue the rich tradition of its past. Years that will see new generations of astronomers push back the frontiers of science. So lift a glass with me to the second centennial of the Mount Wilson Observatory!"

-- Don Nicholson, Associate Deputy Director for Public Affairs, December 20, 2004

Don Nicholson's father, Seth Nicholson, served on the Mount Wilson Observatory staff from 1915 to 1957. Don has been associated with Mount Wilson for more than 80 years.
Photo of Don Nicholson on Mount Wilson in 1935.
Photo of Don Nicholson at the Hale Solar Laboratory in 2004. Photo by Gale Gant.

Historical Highlights from Mount Wilson Observatory's First 100 Years

  • June 13, 1904: George Ellery Hale signs 99-year lease with Mount Wilson Toll Road Company.

  • December 20, 1904: the Carnegie Institution of Washington agrees to fund the "Mount Wilson Solar Observatory."

  • 1905: Snow solar telescope becomes operational at Mount Wilson. Read an article on the founding of the solar program.

  • 1905: Charles G. Abbot of the Smithsonian Institution comes to Mount Wilson to begin long-term studies of the solar constant.

  • 1905: E. E. Barnard comes to Mount Wilson from Yerkes Observatory to photograph the southern Milky Way and diffuse nebulae with Yerkes' Bruce Telescope.

  • 1906: Hale proves that sunspots are actually regions of reduced solar temperature. Read an article on early solar research by Hale's deputy, Walter Adams.

  • 1906: Hale orders glass for 100-inch mirror from Saint-Gobain glass works in France.

  • 1907: Toll "road" widened to accommodate motorized vehicles.

  • May 28, 1907: First motor car to reach summit (1907 Franklin).

  • 1908: 60-foot solar telescope operational. Browse the historical photo scrapbook.

  • June 25, 1908: Hale detects solar magnetic field with 60-foot solar telescope (first detection of a magnetic field outside the Earth).

  • December 7, 1908: 100-inch mirror blank arrives in Pasadena.

  • December 13, 1908: "First light" for the 60-inch telescope. Read an article about building the 60-inch telescope.

  • March 17, 1910: Andrew Carnegie visits Mount Wilson.

  • August 31-September 6, 1910: International Solar Union conference at Mount Wilson.

  • May 1912: 150-foot solar telescope operational. Read an article on the telescope's history and browse the historical photo scrapbook.

  • May 20, 1912: Fore River Shipyards begins work on the 100-inch telescope's tube and mount.

  • 1914: Hale discovers that sunspots in northern and southern hemispheres of the sun reverse their polarity every 11 years (published in 1925 with Seth Nicholson and later known as the Hale-Nicholson Law).

  • November 1, 1915: First billiard game played on Mount Wilson.

  • January 4, 1917: Daily sunspot drawings in 150-foot tower begin (continued until September 16, 2004).

  • 1917: Harlow Shapley locates galactic center using 60-inch telescope.

  • July 1, 1917: 100-inch mirror arrives at Mount Wilson.

  • November 2, 1917: "First light" for the 100-inch telescope. Read an article about building the 100-inch telescope.

  • December 13, 1920: First stellar diameter (Betelgeuse) measured by Francis Pease and Albert Michelson, using 20-foot interferometer beam on the 100-inch.

  • 1923: Walter Adams succeeds Hale as Observatory director; Hale begins construction of solar laboratory in Pasadena.

  • October 5, 1923: Edwin Hubble finds Cepheid variable star in Andromeda Galaxy (M31).

  • January 1, 1925: Historic paper by Edwin Hubble shows distance to M31, proving that our Milky Way is only one of many galaxies.

  • March 1925: Hale Solar Laboratory in Pasadena completed.

  • 1925-1929: Albert Michelson measures velocity of light by projecting a light beam from Mount Wilson to Lookout Mountain and timing its return.

  • March 15, 1929: Edwin Hubble correlates distance to galaxies with their recessional velocity, confirming the expansion of the Universe.

  • January 29, 1931: Albert Einstein visits Mount Wilson.

  • 1935: Angeles Crest Highway and Red Box-Mount Wilson road opened to the public.

  • February 27, 1935: 100-inch mirror aluminized for the first time, replacing the silvering process formerly used.

  • August 24, 1937: Olin Wilson discovers first Wolf-Rayet star.

  • June 6, 1938: Seth Nicholson discovers 10th satellite of Jupiter with 100-inch (he discovered four Jovian satellites in all, three of them at Mount Wilson).

  • June 18, 1941: Walter Baade discovers remnant of Kepler's 1604 supernova.

  • November 10, 1942: Edison Pettit discovers Nova Puppis.

  • Circa 1944: Walter Baade, confined to Mount Wilson as a resident alien during WWII, classifies stellar populations.

  • 1952: Harold and Horace Babcock invent solar magnetograph, first installed at Hale Solar Laboratory.

  • 1957: Solar Magnetograph installed at 150-foot tower.

  • 1962: Robert Leighton, Robert Noyes, and G. Simon discover the 5-minute solar oscillations.

  • 1965: Robert Leighton, Gerry Neugebauer, and Dowell Martz conduct the first infrared sky survey, using a 60-inch f/1 reflector constructed for this purpose at Mount Wilson.

  • 1966: Olin Wilson begins long-term observing program to measure "starspot" cycles of stellar magnetic activity (HK Project).

  • 1977: HK Project moved from 100-inch to 60-inch and automated with HK photometer designed by Arthur Vaughan.

  • 1978-79: Arthur Vaughan and George Preston discover "Vaughan-Preston gap" in H and K fluxes of stars plotted against their colors.

  • 1980: Robert F. Howard and Barry J. LaBonte discover the torsional oscillations of the sun using 150-Foot solar telescope.

  • June 1981: American Society of Mechanical Engineers (ASME) places plaque beside the 100-inch telescope designating it a mechanical engineering landmark.

  • April 1, 1981: First woman hired as a telescope operator at Mount Wilson (Laura Woodard for HK Project on 60-inch).

  • June 1985: Carnegie Institution closes 100-inch telescope and withdraws financial support from Mount Wilson Observatory.

  • February 26, 1986: Mount Wilson Institute (MWI) incorporated.

  • September 20, 1986: "First fringes" for U.S. Naval Observatory's Mark III stellar interferometer.

  • June 29, 1988: "First fringes" for Charles Townes' UC Berkeley Infrared Spatial Interferometer (ISI).

  • January 5, 1989: Carnegie turns over management of Mount Wilson Observatory to MWI.

  • 1990: Consortium for Undergraduate Research and Education in Astronomy (CUREA) summer program begins at Mount Wilson.

  • 1992: The Atmospheric Compensation Experiment (ACE), an early adaptive optics system on loan from the Department of Defense's Strategic Defense Initiative (SDI), is mounted on the 60-inch telescope.

  • August 21, 1993: First remote operation of Telescopes In Education (TIE) 24-inch telescope at Mount Wilson.

  • October 3, 1993: Renovated Snow solar telescope rededicated on its 90th birthday.

  • 1995: First visible-light adaptive optics (AO) system installed on the recommissioned 100-inch.

  • 1995: Georgia State University selects Mount Wilson as site for CHARA stellar interferometer array.

  • June 13, 1996: CHARA array groundbreaking ceremony.

  • June 21, 1997: First UnISIS laser propagation into atmosphere for 100-inch laser-guidestar adaptive optics system.

  • November 23, 1999: "First fringes" for Georgia State's CHARA array.

  • September 6, 2000: Third telescope added to ISI infrared interferometer array.

  • October 4, 2000: Dedication ceremony for CHARA array.

  • September 20, 2001: "First fringes" over longest (331m) CHARA baseline.

  • 2003: Mount Wilson Observatory's 99-year lease renewed (with present landowner, the U.S. Forest Service).

  • December 20, 2004: Mount Wilson Observatory marks the end of its first century of operation.
Other Pages Related to the Centennial

In 1903
A poem about the first visit of George Ellery Hale, founder of Mount Wilson Observatory, and William Campbell, Director of Lick Observatory, written by early Mount Wilson staff member Harold Babcock. The poem is based in part on Hale's own verbal account of the trip to the author.

The Astronomical Society of the Pacific (ASP) has awarded its highest honor, the Catherine Wolfe Bruce gold medal, for lifetime contributions to astronomy most years since 1898. This is a list of Mount Wilson staff who have won this prestigious award with links to their biographies on J.S. Tenn's Bruce Medalists website.

BBC News article on Mount Wilson's centennial
An article by BBC News about Mount Wilson Observatory's centennial.