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Backstaff
The backstaff has a lignum vitae frame and boxwood scales, an inlaid ivory plate on the main strut, brass rivets, and no vanes. Decorative stars and fleurs-de-lis are stamped on the frame and handle.
The transversal scale on the thirty degree arc (cracked) is from 0° to 25° by 5 arcminutes and reads to 1 arcminute. The graduation on the sixty degree arc is from 0° to 65° 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 (cracked) is from 0° to 25° by 5 arcminutes and reads to 1 arcminute. The graduation on the sixty degree arc is from 0° to 65° 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: | NAV0035 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Backstaff |
| Display location: | Not on display |
| Creator: | Gilbert & Sons |
| Date made: | 1755 |
| People: | Norman, J |
| Credit: | National Maritime Museum, Greenwich, London, Caird Collection |
| Measurements: | Overall: 16 mm x 639 mm x 355 mm |
| Parts: | Backstaff |