F6820-001

Sextant Long Caption: Brass frame, wooden handle. Signed on the bottom of the limb ' Nairne & Blunt, London', and marked 'I [foul anchor] R' stamped at the centre of the scale (at 77°). Scale on bronzed limb from -3° to 139° by 20', measuring to 124°. Vernier to 30'', zero at right. Tangent screw (bent) on top of the index arm, clamp screw on the back. The index glass is fitted with a Maskelyne flap. Three shades (red, red, green), one horizon shade (red). Index glass adjustment by screw, horizon glass by extended lever and clamp operated from beneath the telescope bracket (Peter Dollond's 1772 patent). Telescope bracket in two parts, fitted for correcting collimation error, and perpendicular adjustment by rising piece. Telescope (129 mm), erect image and two parallel wires. Radius 12'' (305 mm). The Maskelyne flap consists of a hinged brass flap that can be used to obscure the lower (silvered) half of the index glass. The index arm is inscribed: 'Once the Property of Admiral Sir John Thomas Duckworth, K.C.B., Bart. of Wear B. 1748, D. 1817'. Credit line: © National Maritime Museum, Greenwich, London Object: NAV1110 Artist: Nairne & Blunt Date: circa 1780 Medium: brass; bronze; wood; glass Size: 110 mm x 380 mm x 358 mm Click here to buy a bespoke print of this image.