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Octant
The octant has a mahogany frame and limb with a brass index arm and fittings, and an inlaid ivory plate on the crossbar. There is no tangent screw and the clamping screw is on the back of the index arm. The shades for the octant’s sockets are missing. Index-glass adjustment is made by a screw and on the horizon glass by a lever, wing nut, and a milled clamping screw. The sight vane is missing. The octant has no box.
The instrument has an inlaid ivory scale in two sections (joined at 50°) from -3° to 93° by 20 arcminutes, measuring to 93°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the centre.
It was made by Edward Nathaniel Sweeney or by his widow.
The instrument has an inlaid ivory scale in two sections (joined at 50°) from -3° to 93° by 20 arcminutes, measuring to 93°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the centre.
It was made by Edward Nathaniel Sweeney or by his widow.
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Object Details
| ID: | NAV1351 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Octant |
| Display location: | Not on display |
| Creator: | Sweeny |
| Date made: | ca.1750; ca.1780 |
| Credit: | National Maritime Museum, Greenwich, London, Oliver Hill Collection |
| Measurements: | Overall: 69 mm x 400 mm x 345 mm |