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Octant
The octant has an ebony frame and limb with a black-lacquered brass index arm and fittings. It has inlaid ivory plates on the crossbar and on the back of the frame. The tangent screw and clamping screw, which is a replacement, are located on the back of the index arm. The octant has three index shades, two red and one green. Index-glass adjustment is made by a screw and on the horizon glass by a lever, worm gear and a milled clamping screw. The sight vane has one pinhole. An ivory cap for a pencil is fitted in the crossbar. The octant has no box.
The instrument has an inlaid ivory scale from -8° to 106° by 20 arcminutes, measuring to 93°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.
The instrument has an inlaid ivory scale from -8° to 106° by 20 arcminutes, measuring to 93°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.
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Object details
| ID: | NAV1322 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Octant |
| Display location: | Not on display |
| Creator: | Unknown |
| Date made: | circa 1825 |
| Credit: | National Maritime Museum, Greenwich, London, Adams Collection |
| Measurements: | Overall: 80 mm x 300 mm x 240 mm |