Original Equipment

Repsold Meridian Transit

The Repsold Meridian transit, 1876

The 7" Clark refractor of the Hopkins Observatory, 1851

The 7″ Clark refractor of the Hopkins Observatory, 1851

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Some of the original equipment from the 1834 trip to England still survives in this building, including a transit, a regulator, and a rule. Transits are astronomical telescopes used to measure when a star transits the meridian, the north-south line that also passes through the zenith. The Troughton & Simms meridian transit is now hanging on the wall in the west wing. This transit was replaced in 1876 by the larger transit, which is now on display 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. The regulator is like a grandfather clock and is an accurate mercury-compensated pendulum timekeeper. A jar of mercury is located at the bottom of the pendulum; its expansion and contraction compensates for the changes in the length of the pendulum that result from changes in temperature.