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