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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 astrolabe, which is a precursor to the sextant, [1] is effective for determining latitude on land or calm seas. Although it is less reliable on the heaving deck of a ship in rough seas, the mariner's astrolabe was developed to solve that problem.
The first known mural sextant was constructed in Ray, Iran, by Abu-Mahmud al-Khujandi in 994. [1] To measure the obliquity of the ecliptic, al-Khujandī invented a device that he called al-Fakhri sextant (al-suds al Fakhrī), a reference to his patron, Buwayhid ruler, Fakhr al Dawla (976–997).
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 ...
Canterbury Astrolabe Quadrant: medieval astrolabe found in England; Celatone: navigational aid reliant on tracking Jupiter's moons in the sky; Celestial sphere: imaginary sphere of arbitrarily large radius, concentric with the observer; Charge-coupled device: device for the movement of electrical charge
The astrolabe/almucantar quadrant – a quadrant developed from the astrolabe: This quadrant was marked with one half of a typical astrolabe plate as astrolabe plates are symmetrical. A cord attached from the centre of the quadrant with a bead at the other end was moved to represent the position of a celestial body (sun or a star).
An astrolabe from the Mughal era exhibited at the National Museum in New Delhi, India. Yantrarāja is the Sanskrit name for the ancient astronomical instrument called astrolabe . It is also the title of a Sanskrit treatise on the construction and working of the astrolabe composed by a Jain astronomer Mahendra Sūri in around 1370 CE.
The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude (declination) or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with an alidade used to measure ...