Description
Although Robert Stewart Whipple purchased his first antique instrument in 1913, it was not until the 1920s that his collection really began to grow. This octant is one of the first hundred objects that Whipple acquired, and demonstrates the early development of his taste for historic scientific artefacts and books.

The octant was purchased in Bath in May 1922 for 10 shillings. A note in Whipple's accession register indicates that his cheque was never cashed!
07/10/2025
Created by: Hannah Price on 07/10/2025

Description
John Hadley, an English seafarer, invented the octant (also called a Hadley quadrant) during the 1730’s. It was used to find latitude by measuring the altitude of the sun, moon or stars.

An octant is an angle of 45°, or an eighth of a circle. The octant was first made with mahogany frames and scales on inlaid boxwood. By the early 19th century ebony (a much more hard wearing wood) had replaced the mahogany to craft the frames which had brass index arms.

The octant is used in a similar way to a sextant. The observer raises the octant until the horizon can be seen through the horizon glass. The index arm and attached index glass are moved until the twice-reflected image of the sun or star can be seen superimposed on the horizon, enabling an angle to be read off.

The octant was inexpensive and became the everyday instrument for measuring latitude, whilst the more expensive sextant was used to find longitude by measuring lunar distances.

Created by: Corrina Bower