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By the end of the American Civil War, the Observatory's clocks were linked via telegraph to ring the alarm bells in all of the Washington, D.C. firehouses three times a day. The USNO held a one-off time-ball re-enactment for the year-2000 celebration.
Twilight occurs according to the solar elevation angle θ s, which is the position of the geometric center of the Sun relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (nearest the horizon), nautical twilight, and astronomical twilight (farthest from the horizon).
Two sample pages of the 2002 Nautical Almanac. The Nautical Almanac has been the familiar name for a series of official British almanacs published under various titles since the first issue of The Nautical Almanac and Astronomical Ephemeris, for 1767: [1] this was the first nautical almanac to contain data dedicated to the convenient determination of longitude at sea.
Two sample pages of the 2002 Nautical Almanac published by the U.S. Naval Observatory. A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation to determine the position of their ship while at sea.
From 1865 to 1884, the Bureau was responsible for the Office of Detail, which handled the assignment and detailing of naval officers. That Office had been established in March 1861, just prior to the outbreak of the Civil War, in the Office of the Secretary of the Navy. The Office of Detail reverted to the Secretary's office on October 1, 1884 ...
The Old Naval Observatory is a historic site at 23rd and E Street in Northwest, Washington, D.C. It is where the United States Naval Observatory was located from 1844 to 1893, when it moved to its present grounds. The original observatory building, built 1839-40, still stands, and is a designated National Historic Landmark as of 1965. [2]
On October 23, 1871, Tuttle independently recovered periodic comet 8/P1871 T1 Tuttle at the U.S. Naval Observatory in Washington, D.C. In 1871 Tuttle served under Commodore George Dewey as astronomer on the survey of the coast of lower California. In 1872 he was assigned to the oceanographic survey ship Lackawanna at Hong Kong. On January 26 ...
Twilight, the period in the morning during which the sky is brightening, but the Sun is not yet visible. The beginning of morning twilight is called astronomical dawn. The period after the Sun rises during which striking colors and atmospheric effects are still seen. [5] Civil twilight being the brightest, while astronomical twilight being the ...