US Naval Observatory

US Naval Observatory information

Washington, DC , USA
3450 Massachusetts Ave NW
+1 202 762 1467
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Opening hours
tours by reservation 8:30pm Mon
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If you’re ever late to an appointment after visiting this place, you’ve got no excuse, buddy: the Naval Observatory is the official source of time for the US military and by extension, the country, so you know the clocks are precise. Framed by a pair of stately white ship’s anchors, the observatory, created in the 1800s, is here ‘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.’

Modern DC’s light pollution prevents important observational work these days, but that cesium-beam atomic clock is still tickin’. Tours let you peek through telescopes and yak with astronomers, but they fill up weeks in advance, may be cancelled at any time and are only offered on select Mondays at 8:30pm (7:30pm from November to February), so reserve early – check the website or phone. On observatory grounds above Massachusetts Ave NW 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.