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Astronomical Adventures

Observatories: The Elgin National Watch Company Observatory

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What is today known as the Elgin U-46 Planetarium began life in 1910 as the Elgin National Watch Company Observatory. By the turn of the century, one of the demands of the Industrial Revolution was the need for increasingly accurate timekeeping. In 1908, President Theodore Roosevelt directed the U.S. Bureau of Standards to establish tests for the accuracy of watches.

In order to maintain its position as a leading manufacturer of timepieces, the Elgin National Watch Company decided to build an observatory that would measure time more accurately than any other facility in the U.S. The observatory was sited on the top of a hill just east of the watch factory.


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To measure the time, a transit telescope was used to very accurately identify the transit or meridian (due-south) crossing of stars.

From these observations, the observatory's astronomers were able to accurately determine the local time. To convert these stellar observations into the current time, an instrument called a chronograph was used.

To "store" this information, the Observatory used two Riefler clocks. One of these clocks was kept at sidereal time and the other was set to standard time. These German-built clocks were the most accurate timekeepers of their day.

To further insure the accuracy of these clocks, they were housed in a vault that insulated them from the outside world. To minimize any vibrations that might affect the clocks, each was mounted on a concrete pier that extended down into the ground 60 feet. Temperature variations could also affect the accuracy of the clocks. Therefore, a system of light bulbs was used to maintain the vault at a temperature of 81 degrees Fahrenheit within a plus/minus variation of only 2/10 of 1 degree. Another factor that could affect accuracy was changes in air pressure. To eliminate this problem, the clocks were sealed inside glass housings. To take advantage of the measurable effect of air pressure on the clocks, a system was set up so that air could be pumped into or out of the sealed housings in order to alter the clock's rate of time.

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In all, this timekeeping system made it possible for the observatory to keep track of the time to within ten-hundredths of a second.

In the end, the advances in technology that created the demand for the Observatory also resulted in its demise. The accuracy obtained by the Observatory was eventually surpassed by other more accurate methods of timekeeping, like the atomic clock. As a result, the Elgin National Watch Company closed the doors to its Observatory in 1958. Thus closed the first chapter in the life of the Elgin National Watch Company Observatory. However, two years later the Observatory got a new lease on life when it was donated to the local school system, Elgin U-46 . Thus begins the Observatory's second life as the U-46 Planetarium.

[A more detailed article on the history of the Observatory, written by Gary Kutina, the Elgin U-46 Planetarium Director, can be found in the February 1995 issue of "Historic Illinois."]

Through the efforts of Planetarium Director Gary Kutina, the Elgin U-46 Planetarium was placed on the National Register of Historic Places in August 1994.

Learn more about the
U-46 Planetarium.



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