Hadley's octant. An triangular ebony frame shaped like a section of a circle, with an ivory scale along the curved outer edge. A brass arm with a small scale and a screw at the end reaches from the point of the frame to the outer edge and can be rotated along it. There are three black glass discs in hinged brass frames on one side and the whole instrument stands flat on small brass legs.

ABDNP:200044a

Ebony frame with ivory scale having anchor engraved at its centre, calibrated in degrees, micrometer adjustment & Vernier to 1' arc. 1 green shade, 2 red shades. Double pin-hole site with moveable cover across a single pin-hole. Forerunner of the sextant, the OCTANT is similarly used as a navigational aid to measure angles from which the position of the observer can be deduced. The measurement most commonly taken is the altitude of the sun at noon. This particular octant is likely to be the one recorded as purchased in 1803 for £3.10.0 .

1803

wood, brass, ivory, glass
radius 254 mm

Physical Object