Us Naval Observatory

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  • Address
    3450 Massachusetts Ave NW, Upper Northwest DC
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  • Phone
    762 1438
  • Website

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The US Naval Observatory was created in the 1800s 'to determine the positions and motions of celestial objects, provide astronomical data, measure the Earth's rotation, and maintain the Master Clock for the US.' DC's light pollution prevents important observational work these days, but its cesium-beam atomic clock still sets all standard time in the US. Tours let you peek through telescopes, yak with astronomers and learn about the Master Clock.

Tours fill up weeks in advance, may be cancelled at any time and are only offered on select Mondays at , so reserve early - check the website or phone. At other times the observatory's closed to the public. On observatory grounds above Massachusetts Ave is the official Vice President's Residence (Admiral's House), which is closed to the public. Driving is the best way to reach the observatory.