Antique Octant / marine navigation instrument. From the 19th century

Antique Octant. From the 19th century

The instrument is built according to the so-called Hadley principle (named after Englishman John Hadley, who invented the octant in 1731), where two mirrors allow for measuring angles up to 90 degrees on an arc that only constitutes 1/8 of a circle (45°).

The octant is constructed with a triangular frame of black-painted wood and a long index arm in brass, which moves along the curved scale. The octant is equipped with a horizon mirror and an index mirror in brass holders, as well as a set of colored shadow glasses (dark and turquoise) to dampen sunlight during observations. The scale is executed in bone with nonius reading, operated via a fine-adjustment screw.

Measurements: approx. 25x30,5x7,5 cm.

Condition: incomplete. This is a collectible, and since we are not experts in navigation instruments, we can naturally not guarantee the actual functionality, otherwise see images.