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Titolo dell'opera:
Hadley Octant
Epoca:
Inventario:
1796
Misure:
Tipo di misura: diametro; Unità di misura: cm; Valore: 25,5
Tecnica:
ebano/ avorio/ vetro
Back to Focus:
Descrizione:
The octant is an instrument mainly used in navigation to measure the height of a star on the horizon line, i.e. to determine the latitude of the observer's location.
It owes its name to its 45° sector shape of a circle, the eighth part. On the curved side is an ivory graduated scale. At the centre of the sector is a movable part - the alidade - which ends with 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 “reflecting instrument”. Its invention is attributed to Isaac Newton, although John Hadley (1682-1744) made the necessary modifications to make it an instrument that was carried by every naval officer in the 19th century.
