backstaff

Navigational instrument with rods supporting two scaled arcs, invented by Englishman John Davis in 1594. It was the precursor of the 18thC octant. The observer stood with back to the sun and aligned one scale on the horizon, the other on the shadow cast by its sighting piece. The two scale readings added together gave the sun's height and thus lati …...

Backstaff

The backstaff is a navigational instrument that was used to measure the altitude of a celestial body, in particular the sun or moon. When observing the sun, users kept the sun to their back (hence the name) and observed the shadow cast by the upper vane on a horizon vane. It was invented by the English navigator John Davis who described it in his ...
Found on http://en.wikipedia.org/wiki/Backstaff

Backstaff

• (n.) An instrument formerly used for taking the altitude of the heavenly bodies, but now superseded by the quadrant and sextant; -- so called because the observer turned his back to the body observed.
Found on http://thinkexist.com/dictionary/meaning/backstaff/

backstaff

(from the article `navigation`) ...observer to look directly into the Sun. Coloured shades were fitted to the crosspiece, but the decisive improvement was made in 1594 by the ...
Found on http://www.britannica.com/eb/a-z/b/4

Backstaff

Back'staff` noun An instrument formerly used for taking the altitude of the heavenly bodies, but now superseded by the quadrant and sextant; -- so called because the observer turned his back to the body observed.
Found on http://www.encyclo.co.uk/webster/B/4

backstaff

Invented by englishman john davis in 1594, a navigational instrument supporting two scaled arcs. The precursor of the 18thC octant. The user stood with his back to the sun and aligned one scale on the horizon and the other on the shadow cast by his sighting piece. The two scale readings added together gave the suns height and allowed the latitude t...
Found on http://www.antique-marks.com/antique-terms-b.html
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