United States Naval Observatory

The United States Naval Observatory ( USNO ) is a research institute of the U.S. Navy. It is located in the northwestern part of Washington, DC.


The institute was founded on December 6, 1830. The observatory reached under Simon Newcomb world fame when he presented through high-precision astrometric observations in star and planetary system on the astronomical fundamental system more accurate basis.

In 1870 the observatory was one of the first of a worldwide series of giant telescopes with which the star positions and astronomical fundamentals were elsewhere significantly improved. The USNO telescope had an aperture of 26 "( about 65 cm) and was associated with a focal length of about 10 m was then the largest refracting telescope in the world. With the opening of the new University Observatory Vienna this place went for a few years at the 27- inch refractor about.

The Institute soon became internationally important tasks, such as in the ephemeris and time service at the World length determination in 1933 and the basic questions of navigation.

Today, the USNO one of the central offices of the International Earth Rotation and Reference Systems Service for Service (IERS ).

Flagstaff station

Since 1955, the USNO also operates an observatory in a remote station near Flagstaff, Arizona (35 ° 11 ' 3 " N, 111 ° 44' 25 " W35.184166666667 - 111.74027777778 ). Due to the better Sichtbedinungen here a number of larger and more modern reflecting telescopes are operated:

  • 61- inch or 1:55 - m Kaj beach Telescope
  • 1.3 m ( 51- inch) reflector
  • 1.0 m (40 in ) Ritchey -Chrétien telescope (the first? )

Was further along with the Lowell Observatory in nahegelegenem Anderson Mesa an optical interferometer, the

  • Navy Prototype Optical Interferometer ( NPOI )

Built. This consists of three arms, each 250 m in length, in which can be coupled via vacuum tunnels the light from 6 siderostats with a diameter of 50 cm and combined with an interferometric image extremely high resolution.

Navy Prototype Optical Interferometer in Anderson Mesa

Time signal

The observatory gives off a high-precision time service for military users. Under the announcement phone 1 (202) 762-1401 this time signal is also provided civilian users free of charge.

The Office of the Vice President

Since 1974, Number One Observatory Circle, a building to be used on the grounds of the Naval Observatory as the official residence of the Vice President of the United States.