
This auction has ended. View lot details
You may also be interested in
Lot 7
EARLY SEA CAPTAIN'S BACKSTAFF.
21 September 2015, 13:00 EDT
New YorkSold for US$3,125 inc. premium
Looking for a similar item?
Our History of Science & Technology specialists can help you find a similar item at an auction or via a private sale.
Find your local specialistAsk about this lot


Client Services (New York)

Client Services (San Francisco)

Client Services (Los Angeles)
EARLY SEA CAPTAIN'S BACKSTAFF.
English, 1735, signed "Made by Will Garner for Robert Duesbery 1735." 25" long, in dark hardwood with arcs and plaque in contrasting boxwood. Large arc divided every five arcminutes from 0° to 25°, with a scale of transversals for accurate interpolation. Punched with decorative fleur-de-lys and rosettes. A few chips at old break in small shadow arc, modern replacement sight vanes in light wood.
The backstaff, a great improvement over the cross staff, allowed a navigator to measure the sun's altitude with the sun at one's back, thus saving one's eyesight. It further eliminated the cross staff's problem of parallax and difficulty of simultaneously sighting two widely separated objects (the sun and horizon for example). The maker, William Garner, is known for three other backstaves, dated 1732, 1734, and 1737.
The backstaff, a great improvement over the cross staff, allowed a navigator to measure the sun's altitude with the sun at one's back, thus saving one's eyesight. It further eliminated the cross staff's problem of parallax and difficulty of simultaneously sighting two widely separated objects (the sun and horizon for example). The maker, William Garner, is known for three other backstaves, dated 1732, 1734, and 1737.





![[Americana.]](/_next/image.jpg?url=https%3A%2F%2Fimg2.bonhams.com%2Fimage%3Fsrc%3DImages%252Flive%252F2006-09%252F22%252F7332891-4-1.JPG%26width%3D650&w=2400&q=75)
