United States Naval Observatory

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United States Naval Observatory a federal astronomical observatory , located in Washington, D. C. It evolved from the Navy's oldest scientific institution, the Depot of Charts and Instruments, founded in 1830; the observatory was completed in 1844 and moved to its present site in 1893. It was formerly administered through the Bureau of Navigation and is now under the jurisdiction of the chief of naval operations. The principal instrument at the Washington headquarters is an Alvan Clark 26-in. refracting telescope, which has been in almost continuous operation since its installation in 1873, when it was the largest of its kind in the world. The original mounting and drive were replaced during the 1893 move. Other equipment includes a number of ordinary refracting and reflecting telescopes and special telescopes (photographic zenith tubes) used in the precise determination of time. The observatory's Flagstaff Station in Arizona has 61-in. and 40-in. reflecting telescopes; in 1978, J. Christy discovered Pluto's moon Charon with the 61-in. instrument. The main programs of the Naval Observatory involve continual observations of the positions and motions of celestial bodies for astronomical and navigational purposes and for the derivation and broadcasting of accurate time signals. Atomic clocks, cesium clocks, mercury ion clocks, and hydrogen maser frequency standards are all used for the observatory's time system, which is accurate to within a few billionths of a second per day. Since 1894 the U.S. Naval Observatory has included the Nautical Almanac Office, which publishes the American Ephemeris and Nautical Almanac. The observatory also has an extensive library.

US Naval Observatory (USNO) The US government observatory in northwest Washington, DC. It was founded in 1844, taking over the astronomical work of the US Navy's Depot of Charts and Instruments. It moved to its present site in 1893, absorbing the US Navy's office of The Nautical Almanac. Its main instrument is a 26-inch (0.66-m) refractor, opened in 1873. Since 1955 the USNO has operated an observing station near Flagstaff, Arizona, at an altitude of 2315 m. The instruments here include the 1.55-m Kaj Strand astrometric reflector, opened in 1964; a 1-m reflector moved from Washington in 1955 and given a new mirror in 1969; and a 1.3-m wide-field telescope opened in 1999. USNO also jointly owns and operates the Navy Prototype Optical Interferometer (NPOI) at Lowell Observatory. http://www.usno.navy.mil/

Naval Observatory USNO one of the oldest scientific agencies in the United States, established in 1830 as the U.S. Navy Depot of Charts and Instruments, responsible for the Navy's chronometers, charts, and other navigational equipment. Over the years its mission expanded to include a full range of scientific astronomical research. Today the USNO is the preeminent authority on timekeeping and celestial observation and is responsible for supporting all U.S. Government agencies and the general public with astronomical and time data essential to navigation, communications, and other purposes. The official residence of the Vice President of the United States is located on the Observatory grounds.