The Jacob's Staff

A Predecessor of the Sextant

Already Christopher Columbus was using this ingenious instrument to measure the declination of stars and angular distances of landmarks.

The Jacob's Staff served navigators reliably for a long time before it was superseded by the mirror sextant in the 18th century. This historically accurate, fully functional cardboard replica has a main staff with scales that can be read to one minute accuracy and has 3 transoms that range from 8°, 15°, and 29° to 45°.

This is how to measure angles

Push a transom onto the main staff and place its flat end under the eye on the cheekbone. Slide the transom back and forth until it fits snugly between the two points. If the angle is too small or too large, use a different transom. The angle is measured on the main bar, on the side of the transom facing your eye. Each transom has its own scale printed on the main staff.

For teachers and students

The Jacob's Staff is easy to build and makes excellent teaching material for secondary schools. Like all our Educational Kits, it can also be used for group and project work on the subjects of astronomy and physics.