Quintant made by John Dennett Potter, London, about 1885. Anodized brass diamond-pattern frame, wooden handle. Signed on the limb: J.D. Potter; Poultry & Tower Hill London. Marked at the bottom of the index arm: H O [broad arrow] 10. Inlaid silver scale from -5° to 163° every 10', measuring to 138°. Silver vernier to 10". The tangent screw and clamping screw are on the back of the index arm. Four shades (three grey, one green); three horizon shades (two grey, one green). Index-glass adjustment by screw; adjustment of the horizon glass by capstan screws and a square-headed screw and a detached key. Magnifier on a 90 mm swivelling arm, a frosted glass shade. Threaded telescope bracket in two parts, fitted for correcting collimation error; perpendicular adjustment by rising-piece and a milled knob. Telescope (82 mm) erect image; telescope (184 mm) inverted image, two parallel cross-wires; telescope (155 mm) star finder; extra draw tube (80 mm) inverted image, four cross-wires. Sight-tube (80 mm); three shaded eyepieces (all green); detached threaded telescope bracket for the star finder; adjusting key; adjusting pin. Mahogany keystone box, containing in the lid three certificates of examination of the National Physical Laboratory, for 1885, [illegible, stuck over] and for 1910. The lid also contains a trade label for Cary, Porter Ltd, and a Notice by them explaining how the star finder should be attached to the framed; it was an addition, made by Cary in April 1889. Formerly the property of the Hydrographic Office of the British Admiralty.
Sextant of lattice frame design by J D Potter, Poultry and Tower Hill London, mid 19th century. Later modified with inverting telescope added by Cary, London. Property of the Hydrographic Office of the British Admiralty.
Mahogany case and accessories for Sextant of lattice frame design by J D Potter, Poultry and Tower Hill London, mid 19th century. Later modified with inverting telescope added by Cary, London. Property of the Hydrographic Office of the British Admiralty.
