Timekeeping at the Detroit Observatory
Timekeeping was instrumental in the creation of the University of Michigan's astronomical observatory.
University of Michigan
photographs vertical file
(UBImus C455-86)
Henry N. Walker of Detroit stepped forward to assist Tappan in realizing this vision. Walker independently financed the purchase of the meridian circle telescope (photograph, Bentley Historical Library) because he needed the telescope and a trained astronomer to determine accurate time to aid his business dealings in banking and the railroad. Time was determined using the meridian circle telescope, which tracked stars as they crossed the sky's meridian. Time was then telegraphed from the Observatory to the Michigan Central Railroad Depot so that the precise time could be coordinated across the State. The correct time was very important in keeping trains on schedule, avoiding collisions, and coordinating the time financial markets closed.
Photograph by
Patricia Whitesell
The Detroit Observatory's astronomical clock was made in 1854 by C.F. Tiede of Berlin. It keeps time at the sidereal or "star" rate, which was determined by noting the time between two successive meridian passages of the same star. The sidereal day differs from a solar day by 3 minutes and 56 seconds.
Referring to the time on the Tiede clock, astronomers compared the observed time of the passage of a star with tables of the known times the stars crossed the meridian at Greenwich, England. Greenwich is the zero point for longitude and the basis for universal time. Then a correction was made to the time to account for the distance between the observatory and Greenwich.
Chronometers, which are highly accurate portable clocks, were used to check the time kept by the Tiede clock.
The U.S. Naval Observatory is currently the official source of time for the Department of Defense and the standard of time for the United States.