Mariner’s Backstaff – Clawson Woodworking

Also known as the “Davis Quadrant”

Mariners used the backstaff / Davis Quadrant to measure the sun’s angle from the horizon. This angle, along with published tables on the sun’s position in the sky, allow a ship’s navigator to determine their latitude at sea.

John Davis created the first practical backstaff in 1595 (hence the name Davis Quadrant). Backstaffs became some of the most common navigational instruments in the 17th and 18th centuries because they were easy (in principle) to use, relatively accurate, and fairly inexpensive. Octants replaced backstaffs in the mid-18th century. Sextants, which people today are more familiar with, became the dominant navigational device by the late 18th century.

My backstaff is a based on ones made in North America in the late 17th to mid 18th centuries. The frame is made from iron dyed (ebonized) black walnut. The scales are made of cherry. The vanes are made from African mahogany with brass pressure plates. The entire backstaff is finished with my shop-made linseed oil wax.

I made this backstaff using period joinery and woodworking techniques. The scales are engraved by hand with metal stamped numbers, just like the originals.

If you would like to order a backstaff, please contact me for more details!

Below are detailed images of my backstaff! Click on the images to see higher resolution versions.