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Backstaff
The backstaff is made from a lignum vitae frame with boxwood arcs, and the rivets are capped by decorative ivory triangles. The staff also has a boxwood horizon vane. The sight vane and shadow vanes have brass pressure plates for holding them tightly in place on the arcs and the sight vane has an inlaid copper pinhole sight. The original inlaid plate in the main strut is missing. Decorative stamps are found at the ends of the arcs.
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 65° by 1°, and on the outer edge has a scale for correcting for the Sun’s semi-diameter.
The replacement sight vane and shadow vane, and inlaid blank ivory plate in the main strut, were made in the Museum’s workshop in 1963.
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 65° by 1°, and on the outer edge has a scale for correcting for the Sun’s semi-diameter.
The replacement sight vane and shadow vane, and inlaid blank ivory plate in the main strut, were made in the Museum’s workshop in 1963.
For more information about using images from our Collection, please contact RMG Images.
Object Details
| ID: | NAV0038 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Backstaff |
| Display location: | Not on display |
| Creator: | Wright, William |
| Date made: | circa 1725 |
| Credit: | National Maritime Museum, Greenwich, London, Caird Collection |
| Measurements: | Overall: 125 mm x 640 mm x 357 mm |
| Parts: | Backstaff |
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