From Wikipedia, the free encyclopedia

Aerial view of the U.S. Naval Observatory.

The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States. Located in Northwest Washington, D.C., it is one of the very few observatories located in an urban area; when it was initially constructed, it was far from the light pollution generated by the then-smaller city center.

Number One Observatory Circle, official home of the Vice President of the United States

Established in 1830 as the Depot of Charts and Instruments, it was made into a national observatory in 1842 via a federal law. James Melville Gilliss was put in charge of the project.

The observatory's primary mission was to care for the United States Navy's marine chronometers, charts, and other navigational equipment. It calibrated ships' chronometers by timing the transit of stars across the meridian. Initially located downtown in Foggy Bottom (near the Kennedy Center), the observatory was moved to its present location in 1893, atop Observatory Hill overlooking Massachusetts Avenue, amidst perfectly circular grounds.

The first superintendent was Navy Commander Matthew Fontaine Maury. Maury had the world's first vulcanized time ball, created to his specifications by Charles Goodyear for the U.S. Observatory. It was the first timeball in the United States, and the 12th in the world. Maury kept accurate time by the stars and planets. When the timeball was dropped, a flag was mechanically raised letting all ships and civilians know the exact time. Thus, time was kept not only for Washington, D.C., but, through the use of the telegraph, also for every state in the Union. Time was also "sold" to the railroads and was used in conjunction with Railroad chronometers to schedule American rail transport. Early in the 20th century, the Arlington Time Signal broadcast this service to wireless receivers.

The names National Observatory and Naval Observatory were both used for 10 years, until a ruling was passed to use only the term Navy Observatory. Former President John Quincy Adams had intended for it to be called the National Observatory. John Quincy Adams spent many nights at the observatory with Maury, watching and charting the stars, because it had always been one of Adams' hobbies to study the stars - another reason he passed the bill for the creation of a national observatory just before his leaving presidential office.

In November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless (radio) signals with the United States Naval Observatory, using an antenna in Arlington, Virginia to determine the exact difference of longitude between the two institutions.^[1]

Today, as in the past, the modern United States Naval Observatory continues to be a major authority in the areas of time-keeping and celestial observation. In collaboration with the Rutherford Appleton Laboratory, it determines the timing and astronomical data required for accurate navigation and fundamental astronomy, and distributes this information in the Astronomical Almanac. Perhaps it is best known to the general public for its highly accurate ensemble of atomic clocks and its year 2000 Timeball replacement.

Since 1974, Number One Observatory Circle, a house situated in the grounds of the observatory (formerly the residence of its superintendent, and later the home of the Chief of Naval Operations), has been the official residence of the Vice President of the United States.

As of October 2007, the aerial view of the site is pixelated in Google Earth and Google Maps, while aerial views of the rest of Washington can be seen in high resolution. As of November 2007, the competing Yahoo Maps did not censor this location.

The U.S. Naval Observatory's time service can be accessed by telephone or via the internet. The phone number is (719) 567-6742 in Colorado Springs, or (202) 762-1401 in Washington, DC. On the internet, USNO time service is available at http://tycho.usno.navy.mil/frontpage.html.

• United States Naval Observatory Flagstaff Station
• Navy Prototype Optical Interferometer
• List of observatories
• Rear Admiral Samuel P. Carter

• Sky and Ocean Joined – The U.S. Naval Observatory 1830-2000 by Steven J. Dick (2003) ISBN 0-521-81599-1

• U.S. Naval Observatory.
• USNO, “What Time is it?”
• Transcription: Lieut. Matthew Fontaine Maury’s 1847 Letter to President John Quincy Adams on the many details of the United States Naval and National Observatory.. Archived from the original on 2006-03-21.

• United States Naval Observatory is at coordinates 38°55′17″N 77°04′01″W / 38.921473, -77.066946Coordinates: 38°55′17″N 77°04′01″W / 38.921473, -77.066946