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Backstaff
A lignum vitae frame backstaff with boxwood arcs, brass rivets capped by decorative ivory triangles, and no vanes. The inlaid plate in the main strut is missing and there is now a modern ivory replacement. Floral decorations are stamped on the thirty degree arc.
The transversal scale on the thirty degree arc is from 0° to 25° by 5 arcminutes, and reads to 1 arcminute. The graduation on the sixty degree arc is from 0° to 60° by 1°, and on the outer edge has a scale for correcting for the Sun’s semi-diameter.
The transversal scale on the thirty degree arc is from 0° to 25° by 5 arcminutes, and reads to 1 arcminute. The graduation on the sixty degree arc is from 0° to 60° by 1°, and on the outer edge has a scale for correcting for the Sun’s semi-diameter.
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Object details
| ID: | NAV0037 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Backstaff |
| Display location: | Not on display |
| Creator: | Unknown |
| Date made: | circa 1720 |
| Credit: | National Maritime Museum, Greenwich, London, Caird Collection |
| Measurements: | Overall: 15 mm x 640 mm x 335 mm |