U.S. Naval Observatory

_________________________________________________________________________________________A Brief History


The USNO time ball was one of the first systems to enable the Observatory
to support remote users. The ball was dropped at the astronomically determined
instant of Mean Solar Noon in Washington, D.C., which enabled the navigators of ships anchored in the Potomac River to rate their chronometers.


The U.S. Naval Observatory (USNO) is one of the oldest scientific agencies in the country. It was established in 1830 as the Depot of Charts and Instruments with a primary mission to care for the U.S. Navy's chronometers, charts and other navigational equipment.

In 1844, as its mission evolved and expanded, the Depot was reestablished as the U.S. Naval Observatory and was located on a hill north of where the Lincoln Memorial now stands in Washington, D.C.'s Foggy Bottom district. For nearly 50 years, the Observatory remained at the Foggy Bottom location, during which time significant scientific studies were carried out, such as speed of light measurements, the phenomena of solar eclipses and transit of Venus expeditions. The astronomical and nautical almanacs were started in 1855, and in 1877, astronomer Asaph Hall discovered the two satellites of Mars while working for the Naval Observatory.

The U.S. Naval Observatory's historic Building 1, designed by Richard Morris Hunt
and completed in 1893.

However, by the 1890's it was clear that the Naval Observatory had to move out of the city due to unhealthy conditions in the Foggy Bottom neighborhood. In 1893, after nearly 50 years at the site on the Potomac River, the USNO moved to its present location in the hilly terrain north of Georgetown. At that time, this rural site was well outside the city, and the move not only provided better astronomical observing conditions, but also provided an opportunity to rethink old scientific programs and propose new ones. Along with new programs such as daily monitoring of solar activity, the old functions of time keeping and telescopic observations were kept intact when the Observatory moved to the new site. The old Observatory in Foggy Bottom was declared a National Historic landmark in 1966, and is the current home of the Navy's Bureau of Medicine and Surgery.

Today, the U.S. Naval Observatory is the preeminent authority in the areas of time keeping and celestial observing; determining and distributing the timing and astronomical data required for accurate navigation and fundamental astronomy.

The definitive history of the U.S. Naval Observatory is the book Sky and Ocean Joined: The U.S. Naval Observatory 1830 - 2000  by Steven J. Dick (Cambridge, UK, Cambridge University Press, 2002, ISBN 0 521 81599)