The Elgin Observatory

Elgin built an observatory in 1910 to measure time by the stars. The observatory included a a fixed telescope. An operator would observe the transit (meridian crossing) of stars. At the moment of the transit, the observer would press a button activating an electrical relay and setting two Riefler chronographs to exact time.

The chronographs were kept in a separate room which only two people were allowed to enter at a time in order to avoid temperature shifts. The room was heated to a constant 81 degrees by dozens of light bulbs all around the room. Each light bulb had an individual thermastat turning it on and off as needed to maintain temperature. To control air pressure, each chronograph was sealed in a glass enclosure connected to an apparatus allowing air to be pumped in or out as needed.

From Elgin National Watch Co

Using this facility, Elgin was able to accurately measure time to within hundredths of a seconds.

Elgin operated this system until 1958 when technology began providing better methods. Last I knew, the observatory structure still exists today at 312 Watch Street. It is owned by the city and operated by the Elgin school distict as the Elgin U-46 Planetarium.