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A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation.It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies.
Longitude by chronometer is a method, in navigation, of determining longitude using a marine chronometer, which was developed by John Harrison during the first half of the eighteenth century. It is an astronomical method of calculating the longitude at which a position line, drawn from a sight by sextant of any celestial body, crosses the ...
To find the position of a ship or aircraft by celestial navigation, the navigator measures with a sextant the apparent height of a celestial body above the horizon, and notes the time from a marine chronometer. That height is compared with the height predicted for a trial position; the arcminutes of height difference is how many nautical miles ...
John Harrison (3 April [O.S. 24 March] 1693 – 24 March 1776) was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of how to calculate longitude while at sea. Harrison's solution revolutionized navigation and greatly increased the safety of long-distance sea travel.
A chronometer (Ancient Greek: χρονόμετρον, khronómetron, "time measurer") is an extraordinarily accurate mechanical timepiece, with an original focus on the needs of maritime navigation. In Switzerland , timepieces certified by the Contrôle Officiel Suisse des Chronomètres ( COSC ) may be marked as Certified Chronometer or ...
Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is a 1995 best-selling book by Dava Sobel about John Harrison, an 18th-century clockmaker who created the first clock (chronometer) sufficiently accurate to be used to determine longitude at sea—an important development in navigation.
A boxed chronometer is mounted on gimbals attached to its box. A pocket chronometer is in the style of a pocketwatch. "Winding" refers to the number of days that a chronometer kept going before needing rewinding. However, they were all wound at precisely the same time every day, except for the eight-day chronometers which were wound weekly. [22]
Thomas moved to Liverpool to continue working as a watchmaker in 1843, and thence to London in 1854, to buy a one-way ticket to the USA, in search of new and better prospects. Seeing a chronometer in the window of John Fletcher (chronometer makers), he changed his mind about the USA, asking for work and being hired on the spot. [3]