An early navigator's 13 inch double frame sextant by Edward Troughton, signed Troughton, London on the graduated arc and #295 on the frame (dated 1791). The sextant has a brass straight-bar pattern pillar frame. Tangent screw and clamping screw are located on the back of the index arm. The sextant has three shades: two red and one green, and three horizon shades: two red and one green. Index-glass adjustment is made by a screw and on the horizon glass by screws and a thumbscrew. Attached to the sextant is a threaded telescope bracket in two parts, fitted for correcting collimation error. It has perpendicular adjustment by a rising-piece and a milled knob. The telescope is 184 mm in length with an inverted image, two parallel cross wires, and a shaded red eyepiece. Sight-tube is 117 mm in length and has a red shaded eyepiece. The instrument has a polished brass scale from -5° to 153° by 20 arc minutes, measuring to 126° and a brass vernier measuring to 30 arc seconds, with zero at the right. Edward Troughton patented the pillar and plate frame in 1788.
CONDITION: The removable wood handle is missing. No storage box.
From the Edward L. Greenwood Maritime Collection