Back-Staff

The back-staff, or Davis quadrant, was invented in the 1590s by Captain John Davis and had reached its final form by the 1680s. The back-staff eliminated the disadvantages of the cross-staff by allowing the observer to take a sight without looking into the sun. The instrument also simplified the sighting process by allowing the observer to view both the horizon and the shadow of the sun on the horizon vane simultaneously.

A disadvantage of the back-staff was that it could not be used easily for star sights. Despite this limitation, the back-staff remained popular between the years 1600 and 1800. It was the first navigational instrument of any kind produced in America.

For more information, e-mail collections@MarinersMuseum.org.