Six-inch heliometer made in Germany by Georg Repsold, purchased for the Yale Observatory in 1882.

Inset: Notes recorded during the transit of Venus in 1882 by Jefferson Engel Kershner at the Yale Observatory. Measurements of the sun's diameter taken by "observer" Leonard Waldo using the Yale Heliometer. Clock and
barometer readings are recorded throughout these notes.

During the transit four astronomers used five different instruments. One of these was a photoheliograph apparatus, used by R.W. Wilson to photograph the transit onto glass plates, an example of some of the then newest technologies applied to view the transit of Venus in North America.

The director of the observatory, Hubert Anson Newton, established two commercial enterprises to support its research activities: a Horological Bureau and a Thermometric Bureau. Through the horological service, Yale's "astronomer-in-charge" Leonard Waldo sent regular time signals by telegraph to a team of German astronomers observing the transit of Venus in Hartford, Connecticut, enabling them to accurately measure the speed of Venus's transit across the Sun.

Photograph courtesy of Department of Astronomy, Yale University, 1933. Notes courtesy of the Yale Astronomy Library

The Yale Observatory standard thermometer, no. 77, made by Tonnelot a Paris, January 1885. Crystal glass tube.
YPM catalog no. 5.1460

The Yale Thermometric Bureau was, at the time, the only such service of its kind in North America. One benefit was Waldo’s study of thermometer glass, which led him to campaign to prevent newly made clinical thermometers from being sold immediately after manufacture: because glass needs time to return to its natural density after being worked, a thermometer used too soon could give higher than normal readings, leading to incorrect diagnosis and possibly death.

Funding provided by these two services — a Horological Bureau and a Thermometric Bureau — significantly improved the observatory’s ability to obtain better instrumentation for accurate astronomical measurement. In addition to their role at the observatory, these bureaus were important in improving the quality of clocks and thermometers being made in the United States. The Horological Bureau was a subscription service used by New Haven City Hall, Connecticut telegraph exchanges, the railroad and local companies. Watchmakers and clockmakers also paid the bureau to correct their instruments and to issue certificates of verification that guaranteed quality and accuracy.