The sextant has a polished brass frame and limb with a wooden handle. The tangent screw, with its knob missing, is located on the front of index arm and the clamping screw is on the back. The lower part of the index glass is silvered and can be covered by the Maskelyne flap, whereas the upper part is not silvered. The sextant has three red shades and one red horizon shade. Index-glass adjustment is made by a screw and on the horizon glass, with its glass missing, by screws, a Dollond’s extended lever and a clamp operated from beneath the telescope bracket. 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 127 mm in length with an inverted image, which is possibly not original to this instrument. The sextant has no box.

Object Details

ID: NAV1236
Collection: Astronomical and navigational instruments
Type: Sextant
Display location: Display - Pacific Encounters Gallery
Creator: Ramsden, Jesse
Date made: ca. 1770; circa 1772
Exhibition: Ships, Clocks & Stars: The Quest for Longitude
Credit: National Maritime Museum, Greenwich, London. Acquired with the assistance of the National Heritage Memorial Fund.
Measurements: Overall: 425 x 445 x 95 mm

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