U.S. Naval Observatory, Washington, DC

Far from the madding crowd

The U.S. Naval Observatory sits in a perfect circle, 2000 feet across, in what used to be “rural” Washington, DC, far from any houses, roads, light pollution (bad for telescopes), or traffic. Since it moved to its current location in 1893, Washington has expanded to completely surround the Observatory -- but the 2,000 foot circle remains as an isolated refuge from the city.

At the center of the circle are buildings designed to house very accurate, custom built reference chronometers, used to calibrate shipboard chronometers for navigation; these have been replaced by modern atomic clocks. The circular layout placed roads and other sources of vibration as far away as possible.

US Naval Observatory. Looking south from the roof of Building 1. The Washington Monument is at the center just above the tree line. The Observatory sits in a perfect circle, deliberately far from any road, to keep vibrations from affecting the instruments. Photo © Lawrence I. Charters

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The James Melville Gilliss Library in Building 1, with the nation's finest colleciton of celestial navigation books and references. Photo © Lawrence I. Charters

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The spiral stairs lead to the upper deck of the library. Note the plants, subject to a century of debate over their worth in a library. Photo © Lawrence I. Charters

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Chandelier and skylights for the library. The original chandelier could be run by either gas or electricity. The library makes superb use of natural lighting. Photo © Lawrence I. Charters

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The fountain has served since the beginning to provide “natural” humidity and keep books from cracking. Photo © Lawrence I. Charters

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Through this door is a hallway running the length of Building 1. Photo © Lawrence I. Charters

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Main building holding the atomic clock, which sets the critical time standard for use in US navigation, and is also used by millions of computers for coordinating time. The dome is for satellite communications. Backup clocks are located in other buildings on campus. Photo © Lawrence I. Charters

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Looking south towards downtown DC. The Capitol Dome is just to the left of the flag. Photo © Lawrence I. Charters

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Observatory dome for the 26-inch refractor telescope, as seen from the roof of Building 1. Photo © Lawrence I. Charters

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National Cathedral, seen from the roof of Building 1. The Cathedral is at the highest point in Washington. Photo © Lawrence I. Charters

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The Naval Observatory Superintendent’s house (center right, with conical tower), now used by the Vice President. Secret Service uses the carriage houses, center-left. Photo © Lawrence I. Charters

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12-inch refractor telescope atop Building 1, famed for cataloging binary stars used in celestial navigaton. Photo © Lawrence I. Charters

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Light pollution limits the utility of the telescope in modern Washington, but it is still in use today. The scope is mounted on a caisson running through the building, providing stability and dampening the effects of external vibrtation. Photo © Lawrence I. Charters

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Eyepiece and spotter scope for the 12-inch refractor telescope. — Eyepiece and spotter scope for the 12-inch refractor telescope. "12 inch" refers to the diameter of the glass lens, which should also give you a sense of the size of the entire telescope. The scope is so well balanced it can be moved by hand. Photo © Lawrence I. Charters

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The sidewalk represents the Zero Meridian for the United States. The building in the background used to hold chronometers. Until 1883, official US time and navigation were determined from this starting spot. Photo © Lawrence I. Charters

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The 26-inch refractor was used by Asaph Hall to find the two moons of Mars in 1877. — The 26-inch refractor was used by Asaph Hall to find the two moons of Mars in 1877. "26 inch" refers to the diameter of the lens, which should give you a feel for the huge size of this telescope. Photo © Lawrence I. Charters

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When the telescope was moved in 1893, it gained a custom-built building, designed to be as vibration free as possible. Photo © Lawrence I. Charters

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The floor of the 26-inch observatory is a giant elevator, lifting observers up to the lenses. This is the largest elevator in the city. Photo © Lawrence I. Charters

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The atomic clock. The left one shows UTC (world-wide — The atomic clock. The left one shows UTC (world-wide "universal" time); the right is a reference standard uncorrected for the Earth’s rotation. Navigation, especially GPS, must take into account both measurements. Photo © Lawrence I. Charters

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