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Sextant. A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation . The estimation of this angle, the altitude, is known as sighting or ...
The Sextant reading is known as the 'Sextant Altitude'. This is corrected by use of tables to a 'True Altitude'. The actual declination and hour angle of the celestial body are found from astronomical tables for the time of the measurement and together with the 'True Altitude' are put into a formula with the assumed latitude.
A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...
This is a didactic animation to illustrate the use of the marine sextant to measure the Altitude (astronomy) of the Sun at sea. A detailed explanation of the frames is in the image file. The animation appears in the article sextant. Image created by Joaquim Alves Gaspar. Nominate and support. - Alvesgaspar 11:28, 31 October 2006 (UTC) Comment ...
These instruments differ substantially from a navigator's sextant in that the latter is a reflecting instrument. The navigator's sextant uses mirrors to bring the image of the sun, moon or a star to the horizon and measure the altitude of the object. Due to the use of the mirrors, the angle measured is twice the length of the instrument's arc.
Navigational triangle. The navigational triangle or PZX triangle is a spherical triangle used in astronavigation to determine the observer's position on the globe. [1] It is composed of three reference points on the celestial sphere : P is the Celestial Pole (either North or South). It is a fixed point. Z is the observer's zenith, or their ...
Sight reduction. In astronavigation, sight reduction is the process of deriving from a sight (in celestial navigation usually obtained using a sextant) the information needed for establishing a line of position, generally by intercept method . Sight is defined as the observation of the altitude, and sometimes also the azimuth, of a celestial ...
Jean Picard (21 July 1620 – 12 July 1682) was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand . He is principally notable for his accurate measure of the size of the Earth, based on a careful survey of one degree of latitude along the Paris Meridian.