Hadley's Octant

What is an Octant?

An Octant is a measuring instrument used primarily in navigation. The name “octant” derives from the Latin “octans” meaning eighth part of a circle, because the instrument’s arc is one eighth of a circle. It is a type of reflecting instrument.

Two men independently developed the octant around 1730: John Hadley (1682–1744), an English mathematician, and Thomas Godfrey (1704–1749), a glazier in Philadelphia. While both have a legitimate and equal claim to the invention, Hadley generally gets the greater share of the credit. This reflects the central role that London and the Royal Society played in the history of scientific instruments in the eighteenth century.

The octant provided a number of advantages over previous instruments.
1. It provided both longitudinal and latitude measurements that allowed navigation on open seas.
2. The sight was easy to align because the horizon and the star seem to move together as the ship pitched and rolled. This also created a situation where the error in observation enabled less dependency on the observer, as he could directly see both objects at once.
3. With the use of the manufacturing techniques available in the 18th century, the instruments were capable of very accurate readings. The size of the instruments could be reduced with no loss of accuracy.
4. Using shades over the light paths, one could observe the sun directly, while moving the shades out of the light path allowed the navigator to observe faint stars. This resulted in enhanced usability because it made the instrument usable both night and day.

Octants were produced in large numbers into the 19th century. In wood and ivory, their relatively low price compared to the all-brass sextant (which was developed subsequently) made them a popular instrument. The design was standardized with many manufacturers using the identical frame style and components. Different shops could make different components, with woodworkers specializing in frames and others in the brass components.

The octant revolutionized maritime navigation by making a high-quality product that was affordable and simple to use. The Octant allowed countries and individuals to explore, improve global trade and expand industry. More modern devices are enhancements to the functional use and broad adoption of the Octant.

At Octant Innovations, we embody the spirit of the original octant spirit by revolutionizing the deployment of building technology to change the world.