Marine sextant in excellent condition, complete with all the accessories in working order
Marine sextant in excellent condition, with all the accessories in working order, kept in a solid wooden box.
Sextant dimensions: 25 x 22 x 10 cm. Box dimensions: 27 x 25 x 13.5 cm. Please note that this sextant has nothing to do with the many sextants sold on the web at high prices and very low quality.
The operating principle of the sextant: a sextant is an instrument used to measure the angle of an astronomical object above the horizon.
Technically, the measurement is done by collimating the object with the horizon. Angle and time of the measure can be used to calculate a specific position on a map - for example, sighting the sun at noon to estimate the latitude.
The scale of a sextant is 60°, equal to 1/6 of a circle (hence its name), while the octant is a similar device but it has a smaller scale of approximately 1/8 of a circle, or 45°. This instrument was used until 1767, when the first edition of the Nautical Almanac was published. It reported the astronomical coordinates of the moon, that allowed the navigators of that time to identify the current date according to the angle between the sun and the moon. However, this angle sometimes exceeded 90°, making it impossible to use the octant and smoothing the way for the use of the sextant.
The sextant uses the principle of double reflection: if a light ray undergoes a double reflection on the same plane, the angle of deviation is twice that formed by the reflecting surfaces. The frame of a sextant is actually 60°, but it is graduated in order to read directly twice the angle formed by the two mirrors. The sextant replaced the octant in the second half of the 18th century. Until that time, the octant had been the main navigational instrument. Previously, they used the astrolabe and Jacob’s staff.
The item will be packaged with care and sent by trackable shipping.
|Member since:||May 25, 2016|
Please note: some elements on this page have been translated automatically.Nella descrizione l'acquirente diceva che l'oggetto era funzionate. Quando è arrivato l'oggetto si accendeva ma è causa della mancanza di un pezzo è inutilizzabile.
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