Octant with ebony frame and 9-inch radius limb with brass index arm and fittings and inlaid ivory plates on the crossbar and back; made by S.W. Silver and Co, 66 & 67 Cornhill. London, London, 1835-1845. Fitted with ivory vernier and scales measuring to 92°, with screw adjustment for the index-glass and similar for horizon glass with lever, worm gear, and milled clamping screw. The sight vane has two pinholes and a swivelling shutter. A pencil or screwdriver is missing from the crossbar, box not present
Dated to the mid nineteenth century this octant has a wooden frame inlaid with ivory scales and naked-eye sights. Made by S.W. Silver & Company, London this instrument would have been used for navigation on a ship. The octant could be used to find latitude by measuring the height of the midday Sun or a suitable star at night. Longitude could also be found from determining local noon from the maximum height of the Sun and comparing it with a chronometer set to a fixed meridian. The angle between the fixed stars and the Moon could also be measured to discover longitude using lengthy calculations and tables from the Nautical Almanac.
- Object Number:
- natural sciences
- physical sciences
- furnishing and equipment
- measuring device - instrument
- Courtesy of South Kensington Museum (Circulation Department)
Cite this page
We encourage the use and reuse of our collection data.
Data in the title, made, maker and details fields are released under Creative Commons Zero
Descriptions and all other text content are licensed under a Creative Commons Attribution 4.0 licence
Download catalogue entry as json
Download manifest IIIF
Our records are constantly being enhanced and improved, but please note that we cannot guarantee the accuracy of any information shown on this website.