Jacob’s staff

• The Jacob’s staff is a simple device that was first recorded during the 14th century CE as being used in Medieval Europe. It was replaced by the Sextant.
• It was used to measure angles between the Horizon and a celestial body in Celestial Navigation.

To obtain the altitude of a celestial body

• The Jacob’s staff consists of a pole marked with a scale which is held horizontal to the horizon.
• A sliding crossbar is then brought forward until the top meets with the celestial body.
• The position of the crossbar on the scale is then converted to an angle using tables, and gives the altitude.