The sextant has a varnished brass straight-bar pattern pillar frame, with eighteen pillars, and a wooden handle with a brass-lined threaded hole for a second handle or a stand. The tangent screw and clamping screw are on the back of the index arm. The instrument has four green shades and three green horizon shades. Index-glass adjustment is made by a screw and on the horizon-glass by capstan screws.

Attached to the sextant is a magnifier on an 80mm swivelling arm. There is also a threaded telescope bracket in two parts, fitted for correcting collimation error. It has perpendicular adjustment made by a rising-piece and a milled knob. The telescope is 193 mm in length with an inverted image and four cross wires. An extra drawtube is 78 mm long with an inverted image and two parallel cross wires. A second telescope is 83 mm long with an erect image (star finder). It has a rotation shaded eyepiece with three green shades, an adjusting pin, and a piece of chamois leather.

The instrument has a polished brass limb with an inlaid silver scale from -5° to 160° by 10 arcminutes, measuring to 125°. The sextant has a silver vernier measuring to 10 arcseconds, with zero at the right.

The sextant is contained in a wooden keystone box lined with green textile and containing a trade label for George Lee and Son, Portsea (1850-1900), and in the lid a National Physical Laboratory certificate of examination, dated June 1905. An inlaid plate is missing from the lid.

Edward Smith and George Lee and Son worked for George Whitbread. Edward Troughton patented the pillar and plate frame (no. 1644 of 1788).

Object Details

ID: NAV1200
Collection: Astronomical and navigational instruments
Type: Sextant
Display location: Not on display
Creator: Whitbread; Whitbread, George Smith, Edward
Date made: ca.1875
Credit: National Maritime Museum, Greenwich, London
Measurements: Overall: 112 mm x 250 mm x 300 mm
Parts: Sextant

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