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Titolo dell'opera:
Hadley's octant
Epoca:
Inventario:
1303
Misure:
Tipo di misura: diametro; Unità di misura: cm; Valore: 25,5
Tecnica:
ebano/ avorio/ vetro
Descrizione:
The octant is an instrument used primarily in navigation to measure the height of a star on the horizon line, that is, to determine the latitude of the observer's location.
It owes its name to its 45-degree sector shape of a circle, precisely the eighth part. On the curved side is an ivory graduated scale. On the center of the sector is pivoted a movable part-the alidade-that ends in a “window” through which the measurement is read. The star is not observed directly, but by means of an interplay of mirrors, which is why the octant is called a “reflection instrument.” The invention of the octant can be attributed to Isaac Newton although John Hadley (1682-1744) made the necessary modifications to it to make it an instrument in the 1800s for every naval officer.
