United States Naval Observatory

Sponsor The U.S. Naval Observatory dates from 1830 when the Depot of Charts and Instruments was established under the control of the United States 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.

The only major telescope at the UNSNO is the famous 26” Alvan Clark telescope. It is a REFRACTOR-type telescope. This historic telescope didn’t go into operation until 1873, but it had a huge advantage because it was the largest refracting telescope in the world. 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. Telescopes

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 Astronomers

Under the leadership of Matthew Fontaine Maury, the Naval Observatory achieved wide acclaim for advances in astronomy, navigation, and oceanography. In 1877, Asaph Hall used the historic 26-inch Alvan Clark Refractor at the Naval Observatory to discover the two moons of Mars--Phobos and Deimos. Fame

Lowell Observatory

Lowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965.

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