Astronomical and navigational instruments, Celestial navigation

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Astronomical and navigational instruments

Object connections:

Collection Astronomical and navigational instruments, Celestial navigation
ExhibitionsShips, Clocks & Stars: The Quest for Longitude
User collections Captain Cook's Third Voyage by NMMCollections
William Wales by NMMCollections
The Board of Longitude by Richard_Dunn
Gallery locationPacific Encounters Gallery (Floor plans)

Object details:

Object ID NAV1236
Description 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.
Date made circa 1772

Artist/Maker Ramsden, Jesse
Place made London
Credit National Maritime Museum, Greenwich, London. Acquired with the assistance of the National Heritage Memorial Fund.
Materials brass
Measurements Overall: 425 x 445 x 95 mm
  • Sextant (NAV1236)
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