Famous Observatories

Observatory	United States Naval Observatory
Location:	Washington DC, USA
Date:	1844 (23rd & E Street Site), 1893 (34th Street)
Designer:	Richard Morris Hunt (1893)


	Sponsor	The U.S. Naval Observatory dates from 1830 when the Depot of Charts and Instruments was established under the control of the Navy Department to care for chronometers, charts and other navigational equipment. By a Congressional appropriation of 1842 the Depot was re-established in 1844 in new permanent quarters on the knoll north of the present Lincoln Memorial, at 23rd and E Streets NW, in Washington, DC. In 1854 the institution was officially designated the United States Naval Observatory and Hydrographic Office. The Hydrographic office was officially separated in 1866.

	Construction:	The E street site proved to be a poor choice for an astronomical observatory due to the mud flats and swampy land immediately to the south and west and the closeness of the Potomac River which caused foggy conditions. Since the Naval Observatory required a clear atmosphere free from the smoke and heat radiation of nearby buildings, in 1880 the Congress authorized the purchase of a new site. The area chosen was the 73-acre Barber estate in the country north of Georgetown, presently 34th St. and Massachusetts Ave., NW, in Washington, DC. At the time of the purchase the site contained a mansion, stable and many outbuildings. This new site was chosen for the rural character of the estate and the fact that the land had the highest elevation in the Washington, DC, area. The architect for the Naval Observatory was Richard Morris Hunt, who began work on the original nine buildings in the Spring of 1887. By 1893 the new Naval Observatory was in operation. To protect the integrity of the astronomical instruments from unwanted vibrations that would interfere with operations, Congress passed a Joint Resolution August 1, 1894 (28 Stat. L. 588), prohibiting the construction of any highways within the area of a circle described with a radius of one thousand feet from the center of the clock room of the observatory. The circle thus described marks the official boundary of the observatory. In 1988 the District of Columbia Zoning Commission provided further protection for the Naval Observatory by declaring the area immediately adjacent to the observatory as a Naval Observatory Precinct District. The following buildings, designed and constructed under Hunt's supervision, contribute to the significance of the Naval Observatory as a National Historic Landmark. The Main Building, now known as the James Melville Gilliss Building, is 69 feet wide and 307 feet long. This building has two stories and a basement with stone and brick walls , and houses the offices of the Naval Observatory and the Oceanographer of the Navy. The east end of the building has a circular extension with a conical roof that houses the library of the Naval Observatory, while the west end houses a telescope tower for a 12-inch Alvan Clark refractor. The main section of the building and the library extension are covered with dressed stone with Greek classical details and the telescope end with rock-face stone with Egyptian details. The Great Equatorial Building (renamed for astronomer Asaph Hall in 1966) is 46 feet wide and 72 feet long with one story and a basement with stone and brick walls. It houses the famous 26” Alvan Clark Refractor which was completed in 1873. The Clock room is a one-story building 18 x 20 feet with a basement and stone and brick walls. For many years some of the most delicate clocks of the observatory were kept in this room. The clock room is at the exact center of the observatory circle. The two Observers' rooms measure 18 x 20 feet and are found in a one-story frame building on a foundation of masonry. The East Transit Circle and West Transit Circle buildings each measure 30 x 40 feet. Both structures are one-story buildings with iron frames on a foundation of masonry. The West Transit Circle building contains the six-inch meridian (transit) circle used exclusively for astrometry, with horizontal collimators, and north and south meridian marks. The instrument can be easily reversed to remove systematic errors in observations for determining the celestial latitudes of stars. Both circles are accurately divided. The instrument is provided with a motor driven micrometer. This telescope was designed by William Harkness of the observatory staff and built by Warner and Swasey, and mounted in 1897. The East Transit Circle building originally contained a 9-inch transit circle, modified from an older transit circle first used by Simon Newcomb. It was decommissioned in 1945 and was eventually replaced by a new 7-inch transit circle, designed and built at the Naval Observatory. The 7-inch transit circle was relocated to New Zealand in 1984 to begin astrometry observations in the southern hemisphere. Four small wooden structures (marker houses), used to align the transit telescopes, are found to the north of the East and West Transit Circle buildings and are considered to be part of these buildings. The Boiler-house measures 45 x 54 feet and is a three-story building with stone and brick walls and is connected to the main building via a tunnel. The Superintendent's House, designed by architect Leon Dessez, is a three-story brick structure with extensive use of dormers in the Queen Anne style. The house was originally used as the official residence of the Superintendent of the Naval Observatory. It is now used as the official residence of the Vice-President of the United States. No current information concerning this structure is available to the public. The original brick carriage house and stable of the Barber estate, built around 1860, still stands. This building is a two-story brick L-shaped structure 88 feet x 68 feet x 31 feet with steep pitched roof Federal style windows and rooftop ventilating cupolas. The carriage house is now used by the Secret Service. All other structures at the Naval Observatory, including the Simon Newcomb laboratory, gate houses, garages, greenhouses, storage buildings, dormitories and various maintenance facilities, are not part of this nomination and are not considered to contribute to the significance of the Naval Observatory as a National Historic Landmark.

	Telescopes:	The only major telescope at the UNSNO is the famous 26” Alvan Clark Refractor. The historic 26-inch refractor was originally placed in operation in 1873, and at that time it was the largest refracting telescope in the world. In 1892, in preparation for the move to the new Naval Observatory, a new mounting was ordered from the Warner and Swasey Company in Cleveland, Ohio, for the sum of $28,700, since the original mounting design by Clark had been found to be too light. Warner and Swasey also built the 45-foot, 24-ton steel dome that surmounts the rough white Tuckahoe marble exterior of the building. The objective lens of the telescope was installed in June 1893 and the telescope was ready for regular observation by December. An elevator hardwood floor in the observing room moves up and down to facilitate the use of the telescope in different positions. The floor moves through a range of 12 feet from the lower to the upper balcony. It has to be near its lowest point when a star near the zenith is observed. In intermediate positions it can he quickly adjusted to any height from the eyepiece of the telescope. No further major changes were made on the 26-inch refractor until 1958 when an overhaul and maintenance program was initiated. By 1964 the project had done away with the pier platform and its spiral access stairway and the auxiliary telescopes and periscopes which had been used for remote reading of the circles. Also, the mechanical fast and slow-motion rods and clamps were replaced by variable-speed clutches to transmit fast-motion power to the axes, synchro-systems with easily read console dials, and variable speed slow motions. The old clock drive was replaced with an electric one. A new tailpiece was added and an iris diaphragm installed ahead of the objective.

	Astronomers:	The USNO has been the home of many famous Astronomers either as its Director, as staff members or as visitors. In the post-Civil War era leading mathematicians and astronomers such as Simon Newcomb, C. Henry Davis, George William Hill and Asaph Hall won world esteem for their work at the USNO. By far the most famous discovery ever made with the 26” Refractor is undoubtedly is that of the Moons of Mars. Mars has two tiny natural moons, Phobos and Deimos, which orbit very close to the planet and are thought to be captured asteroids. Both satellites were discovered in 1877 by Asaph Hall, and are named after the characters Phobos (panic/fear) and Deimos (terror/dread) who, in Greek mythology, accompanied their father Ares, god of war, into battle. Ares was known as Mars to the Romans When Hall began his quest in early August, he naturally wanted to work alone, so as to receive full credit in the event of a discovery. By great good luck, Holden, his assistant, was invited by Henry Draper to Dobbs Ferry, New York, "at the very nick of time.. Hall began by scrutinizing faint stars at some distance from Mars itself, but each one soon dropped behind the planet, proving it to be an ordinary field star.6 Next he pressed the search closer, "within the glare of light that surrounded [Mars]," using special observing techniques to reduce the glare, such as "sliding the eyepiece so as to keep the planet just outside the field of view, and then turning the eyepiece in order to pass completely around the planet." On the night of August 10, the first on which Hall attempted to examine the inner space near Mars, he found nothing, but the seeing on the banks of the Potomac was horrible that night, and the image of the planet appeared "very blazing and unsteady." He was on the verge of giving up, but his wife Angelina encouraged him to have one more try, and the next night, at half past two, he found a suspicious object which he referred to in his notebook only as "a faint star near Mars." He scarcely had time to secure its position before the fog began rolling in from the Potomac. The next few nights were cloudy. On August 15, the sky cleared at eleven o'clock, but the atmosphere, Hall noted, was still "in a very bad condition." Not until August 16 did he again find the "star near Mars," which proved, in fact, to be the outer satellite. That night he showed the object to another assistant, George Anderson, but told Anderson to "keep quiet" about it. On August 17, while waiting for that satellite to reappear, he discovered the inner one. In closing his observing notes for the night, he remarked: "Both the above objects faint but distinctly seen both by G. Anderson and myself." Hall had by this time "spilled the beans" to Simon Newcomb, and on August 18, Hall and Anderson were joined in the dome by David Peck Todd, Newcomb, and William Harkness. Todd noted: "Seeing extremely bad: still I saw the companion without any difficulty. `Halo' around the planet very bright, and the satellite was visible in this halo." Only then did Hall announce the discovery of the two satellites. Newcomb tried to gain a share of the credit for himself, implying in an article that appeared in the New York Tribune two days after the discovery was announced that Hall had not fully appreciated what he had found until he Newcomb, had worked out the period of revolution from the preliminary observations.

	Fame:	Under the leadership of Matthew Fontaine Maury, the Naval Observatory achieved wide acclaim for advances in astronomy, navigation, and oceanography. In 1877 for example, Asaph Hall used the historic 26-inch Alvan Clark Refractor at the Naval Observatory to discover the two moons of Mars--Phobos and Deimos. Since 1893 the scientific research at the observatory has related primarily to timekeeping and to the determination, maintenance and dissemination of time, and to the determination of the fundamental celestial positions, motions and constants, which collectively comprise the field of astrometry. The United States Naval Observatory is the only institution in the United States where such fundamental observations are made on a regular basis. Scientists in the Nautical Almanac Office combine this data from the astrometry programs with the theories of motion of the solar system to compute the future positions of the sun, moon, and planets. This information, along with star positions, is made available to navigators, surveyors, geodesists, and astronomers, and forms the basis for all of their work. The Naval Observatory is the source of official time used in the United States and has been charged with maintaining the Department of Defence reference for precise time. The fundamental work of the Naval Observatory in the study of astrometry cannot be overemphasized. This astronomical and timing data is essential for accurate navigation and the support of communications on Earth and in space, and is vital to both the Navy and the Department of Defence. This data is used for everything from guiding missiles to determining the distances to other galaxies and is used extensively by other governmental agencies and the public at large. The Old Naval Observatory was made a National Historic Landmark in 1965, more than seventy years after the relocation of the observatory to the Massachusetts Avenue location. The designation of the 23rd and E Street site was based upon its association with Matthew Fontaine Maury, the father of modern oceanography, and leading astronomers and mathematicians such as Simon Newcomb, George William Hill and Asaph Hall, the discoverer of the two moons of Mars in 1877. The fundamental work of the New Naval Observatory since 1893 is in the specialized field of astrometry. For the past century the Navy has conducted astrometry observations from the same site using the same instruments. The period of time involved means that observations made today can be compared with observations made 10, 20 or even 90 years ago. By comparing modern observations with those taken years ago the Navy can accurately chart the positions of the stars and planets with a precision not available anywhere else in the United States. The site, the telescope, the buildings and even the weather patterns are the same. This accuracy of these observations forms a data base upon which the disciplines of astronomy, navigation, geodesy and surveying depend. It was in recognition of the importance of this work that the Congress originally moved the observatory to the Massachusetts Avenue site away from the traffic and congestion of Washington, and established a large boundary containing sufficient buffer land to protect the delicate instruments from the heat and vibrations arising from normal city traffic. For many years the Naval Observatory has been regarded as the American National Observatory. By devoting its research to the science of astrometry, while other American observatories have studied more modern subjects, the Naval Observatory has earned a unique place in the history of American astronomy.



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