The octant has a mahogany frame and limb with a brass index arm, fittings, and a brass stop for the index arm. It also has inlaid ivory plates on the crossbar and on the back of the frame, which is missing. There is no tangent screw and the clamping crew is located on the back of the index arm. The octant has three socket shades, two red and one green. 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 has two pinholes and a swivelling shutter. An unused ivory-capped pencil is fitted in the crossbar. Decorative engravings are found on the index arm. The octant has no box.

The instrument has an inlaid ivory scale from -2° to 99° by 20 arcminutes, measuring to 91°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.

Object Details

ID: NAV1276
Collection: Astronomical and navigational instruments
Type: Octant
Display location: Not on display
Creator: Spencer Browning & Rust
Date made: 1791
Exhibition: Ships, Clocks & Stars: The Quest for Longitude
Credit: National Maritime Museum, Greenwich, London, Caird Collection
Measurements: Overall: 70 x 375 x 440 mm

Your Request

If an item is shown as “offsite”, please allow eight days for your order to be processed. For further information, please contact Archive staff:

Tel: (during Library opening hours)

Click “Continue” below to continue processing your order with the Library team.