Spanish sextant (late eighteenth century). Sextant. Exhibitions: Discover the sea (permanent exhibition in the Spanish pavilion, Expo'98 Lisbon. Organized by the fifth centenary state society, 22-5 / 26-7-1998) / 1802. Spain between two centuries and the recovery of Menorca. Mahón (8-08 / 30-11-2002) and Archaeological Museum of Madrid (20-12-2002 / 15-03-2003) The sextant is a light and easy transport goniometer, which is mainly used on ships to measure distances Angular and Astros heights in order to determine the latitude of the place. By obsevating a star, from which we know its coordinate
Spanish sextant (late eighteenth century). Sextant. Exhibitions: Discover the sea (permanent exhibition in the Spanish pavilion, Expo'98 Lisbon. Organized by the fifth centenary state society, 22-5 / 26-7-1998) / 1802. Spain between two centuries and the recovery of Menorca. Mahón (8-08 / 30-11-2002) and Archaeological Museum of Madrid (20-12-2002 / 15-03-2003) The sextant is a light and easy transport goniometer, which is mainly used on ships to measure distances Angular and Astros heights in order to determine the latitude of the place. By obsevating a star, from which we know its coordinates, measuring its height with respect to the horizon we can solve the position triangle or, if we observe said star at the time its height is maximum -a moment that will correspond to its passage through the meridian - , the calculation is reduced to a simple algebraic sum of the decline of the star with the height measured with this device. The instrument consists of a metal frame in the form of a circular sector of 60º of amplitude. In its anterior face a limbo that is usually made of silver is recessed, on which the alidada slips, which revolves around the zero center of the limbo. The alidada carries at its end a Nonian that moves graduated, and to fix the device is provided with a pressure screw and a coincidence. Perpendicular to the plane of the limbo are the mirrors: one attached to the alidada and another to one of the arms of the frame, they have half transparent and the other azogada. The other arm of the frame is attached an astronomical glasses whose collimation axis is parallel to the limbo plane. SERIE: Astronomical instruments/latitude
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Photo credit: © EU/BT / Alamy / Afripics
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