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The cosine of the hour angle (cos(h)) is used to calculate the solar zenith angle. At solar noon, h = 0.000 so cos(h) = 1, and before and after solar noon the cos(± h) term = the same value for morning (negative hour angle) or afternoon (positive hour angle), so that the Sun is at the same altitude in the sky at 11:00AM and 1:00PM solar time. [5]
In order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the Greenwich Hour Angle (Celestial Longitude - measured in a westerly direction from Greenwich) and Declination (Celestial Latitude - measured north or south of the equational or celestial equator), of the observed celestial body is ...
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.
Horology & carpentry. 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 ...
In celestial navigation, lunar distance, also called a lunar, is the angular distance between the Moon and another celestial body. The lunar distances method uses this angle and a nautical almanac to calculate Greenwich time if so desired, or by extension any other time. That calculated time can be used in solving a spherical triangle.
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. The Almanac specifies for each whole hour of the year the position on the Earth's surface (in declination and Greenwich hour ...
Retrieved from "https://en.wikipedia.org/w/index.php?title=Greenwich_hour_angle&oldid=713776981"
A culminating star on the observer's meridian is said to have a zero hour angle (0 h). One sidereal hour (approximately 0.9973 solar hours) later, Earth's rotation will carry the star to the west of the meridian, and its hour angle will be 1 h. When calculating topocentric phenomena, right ascension may be converted into hour angle as an ...