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Crow's Patent Seaman's Octant
A computing instrument constructed in the form of an octant, with a curved index scale (90 degrees) and vernier. The right-hand limb is divided with s scale from 0 to 100. A second limb is set at right angles and can slide along the first. It is divided 10 to 70. The index is also divided 0 to 100. The instrument can be used to make calculations using sines, tagents and secants. The instrument is engraved with the words, 'Crow's Patent Seaman's Octant / London'.
An accompanying leaflet (NMM library PBF8050) decribes possible uses of the instrument for navigational calculations, which include: miles in a degree of longitude at any given latitude; meridional difference; difference of longitude; course and distance; plane, traverse and middle distance sailing; parallel, current and windward sailing. The leaflet say the instrument is made and sold by William Crow.
An accompanying leaflet (NMM library PBF8050) decribes possible uses of the instrument for navigational calculations, which include: miles in a degree of longitude at any given latitude; meridional difference; difference of longitude; course and distance; plane, traverse and middle distance sailing; parallel, current and windward sailing. The leaflet say the instrument is made and sold by William Crow.
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Object details
| ID: | NAV0125 |
|---|---|
| Type: | Navigational computing instrument |
| Materials: | Brass |
| Display location: | Not on display |
| Creator: | Crow, Francis |
| Date made: | circa 1832 |
| Credit: | National Maritime Museum, Greenwich, London |
| Measurements: | Overall: 80 mm x 360 mm x 340 mm |
| Parts: | Crow's Patent Seaman's Octant |