Brass framed sextant with stand, artificial horizon and case.

Brass lacquered sextant with straight-bar-pattern, 24 pillar frame, polished brass limb, wooden handle with counterbalanced tripod pillar stand and mercury artificial horizon in wooden box, all by John and Edward Troughton, 136 Fleet Street , London, England, 1790-1800. Consists of brass 127° scale (-5° to 140°) with 20’ divisions and brass vernier (10”), three index-filter shades (red & green), two horizon filters (red & green), scale magnifier on 90mm swivelling arm. Fitted with threaded telescope bracket for sighting telescope (182mm – inverted image) with 2 extra draw tubes, 131mm sighting tube and other accessories. The fitted rectangular case has in the lid the trade card for J. & E. Troughton. The artificial mercurial horizon consisting of a rectangular wooden trough fitted in a tin tray and a brass-framed, roof-shaped cover with glazed side panels, unsigned, made later, 1845-55.

Dated to the late eighteenth century, this brass sextant was made by the London instrument makers, John and Edward Trougton. With its tripod stand and telescopic sights, it was designed for use in navigation, surveying and hydrography. The sextant could be used to find your latitude by measuring the height of the midday Sun or a suitable star at night. Longitude could also be found from determining local noon from the maximum height of the Sun and comparing that time with a chronometer set to a fixed meridian. The angle between the fixed stars and the Moon could also be used to find longitude after lengthy calculations using tables in the Nautical Almanac.

Details

Category:
Astronomy
Object Number:
1931-95
Materials:
brass, glass, lead and wood
Measurements:
overall (estimate): 530 x 430 x 310 mm
type:
sextant, artificial horizon - mercury and instrument case
credit:
Col. A.W. Bentley.

Parts

Case for Brass framed sextant with stand.

Case for Brass framed sextant with stand.

Case for 12-inch pillar sextant, with brass stand, artificial horizon and wooden mercury bottle

Measurements:
overall: 200 x 435 x 370 mm
Materials:
mahogany and incomplete
Object Number:
1931-95 Pt1
type:
instrument case
Image ©
The Board of Trustees of the Science Museum
Brass framed sextant with stand.

Brass framed sextant with stand.

Pillar sextant, 12-inch radius by J. and E. Troughton, London with brass tripod stand.

Materials:
brass , lead , steel , glass and complete
Object Number:
1931-95 Pt2
type:
sextant
Artificial mercury horizon for sextant.

Artificial mercury horizon for sextant.

Artifical horizon (roof type) with boxwood mercury bottle for Pillar sextant, 12-inch radius by J. and E. Troughton, London.

Materials:
brass , boxwood and complete
Object Number:
1931-95 Pt3
type:
artificial horizons (mercury)
Sextant component

Sextant component

Sextant component

Object Number:
1931-95 Pt3/1
type:
component
Image ©
The Board of Trustees of the Science Museum
Part of:
1931-95 Pt3
Sextant component

Sextant component

Sextant component

Object Number:
1931-95 Pt3/2
type:
component
Image ©
The Board of Trustees of the Science Museum
Part of:
1931-95 Pt3