From an Astronomical History...

The Hopkins Observatory is the oldest existing observatory in the United States. In 1834, Prof. Albert Hopkins went to England, with the permission of the trustees of the college, to search for astronomical apparatus. On his return, Prof. Hopkins enlisted some of his students to build a permanent observatory, which they constructed by hand from 1836 to 1838. That building is now the planetarium. It was originally located in the center of the quad; it was moved to the far end in 1908 and to its present location in 1961.

Some of the original equipment from the 1834 trip to England still survives in this building. These pieces are a transit, a regulator, and a rule. Transits are astronomical telescopes used to measure when a star transits, or crosses the meridian, the line from north to south through the point overhead. The Troughton & Simms meridian transit is now hanging on the wall in the west wing. It used to sit on two marble piers, which we do not have on display. This transit was replaced in 1876 by the larger transit in the east wing. The larger transit was used to compile a book of positions of stars called The Williams College Catalogue of North Polar Stars in 1888. The transit was used with the Molyneux and Cope regulator, which was also part of the original equipment brought from England. It is like a grandfather clock and is an accurate pendulum timekeeper. Ours has a mercury-compensated pendulum. A jar of mercury is placed at the bottom of the pendulum; its expansion and contraction compensates for the changes in the length of the pendulum due to temperature. In 1852, the Cambridge, Massachusetts, firm of Alvan Clark built a 7 refracting telescope, which replaced the earlier telescope upstairs. It was restored for the Observatorys sesquicentennial and has been refurbished. The main telescope of the Hopkins Observatory is a 24 reflector which is located on the roof of the physics and astronomy building.

The domed ceiling of the Planetarium was originally black with stars painted on it. In 1963, the projector was installed and is named in memory of Prof. Willis Milham, professor of astronomy from 1901 to 1942 and the third director of the observatory. His predecessor, Truman Henry Safford, was known as a child computing prodigy. His portrait hangs in the east room. The side rooms were turned into the Mehlin Museum of Astronomy in memory of Theodore Mehlin, fourth director of the planetarium and professor of astronomy at Williams from 1942 to 1971.

The Field Memorial Professorship, founded in 1866, was occupied by Prof. Hopkins until 1872. Current Williams faculty are Jay M. Pasachoff, Field Memorial Professor, Director of Hopkins Observatory and Chair of the Department; Karen B. Kwitter, Professor of Astronomy; and Steven Souza, Ph.D., Instructor of Astronomy and Observatory Supervisor.

The Milham Planetarium is supported in part by the Brandi Fund.

James Voelkel, Visiting Assistant Professor of Astronomy, produced an excellent pictorial history in 1994.