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Backstaff

Date: mid-18th century
Dimensions:
Overall: 650 x 355 mm, 0.62 kg
Medium: Lignum vitae, boxwood, ivory
Credit Line: ANMM Collection
Classification:Tools and equipment
Object Name: Backstaff
Object No: 00040037

User Terms

    Description
    This Davis backstaff was designed to measure the altitude of the sun and determine latitude. Its innovative design allowed the user to measure the height of the sun without looking directly at it, saving the eyesight of many navigators! It was constructed from lignum vitae and boxwood, with scales divided over one side and an inset of ivory plate. This version of the backstaff could measure the sun's altitude up to 65 degrees.

    SignificanceThe Davis backstaff represents equipment used for maritime navigation and exploration between the 16th and 18th centuries. It was the technological link between the astrolabe and the development of the reflecting quadrant.
    HistoryJohn Davis is regarded as one of the finest English seamen of the Elizabethan era. He was a notable explorer and navigator who made three voyages in search of the North-West Passage in 1585, 1586 and 1587. He commanded the BLACK DOG against the Spanish Armada in 1588 and in 1591 discovered the Falkland Islands. Davis was also master of Sir Walter Raleigh's flagship in the expedition against Cadiz, and later sailed to the East Indies for the Dutch and English. He was killed in 1605 near Sumatra.

    Davis invented the first backstaff around 1595 and the instrument was to remain in common use until the invention of the reflecting quadrant in 1731 by Hadley. The backstaff was designed to measure the altitude of the sun without the need to sight the sun directly. It initially consisted of a graduated staff with an arc, which could be moved along the staff to measure altitudes up to 45 degrees. Later versions made during the early 18th century could measure up to 65 degrees. This model was the technological link that led to the development of the reflecting quadrant.
    Additional Titles

    Web title: Davis backstaff

    Primary title: Backstaff

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