Instruments

Question 1

The quadrant

Answer 1

A wooden quarter circle held vertically with a plumb line, was probably used on land centuries before it was used at sea

Question 2

The astrolabe

Answer 2

Invented around the 3rd century BC, was a complex instrument for measuring the zenith distance of stars. Its use at sea was limited by the nation of the ship, which prompted navigators to use the horizon as a reference

Question 3

The cross-staff

Answer 3

Invented in the 16th century, was the first instrument to use the visible horizon for celestial observations. The navigator aligned the lower end of the instrument with the horizon and the upper end with the celestial body, and then read the altitude on the scale

Question 4

The backstaff

Answer 4

Or davis quarter, Invented in 1590, allowed the navigator to stand with his back to the sun and align his shadow with the horizon to determine the zenith distance of the sun

Question 5

The nocturnal

Answer 5

Developed around the same Time than the backstaff, provided the sailor with correction to be made to the altitude of the north star to determine latitude

Question 6

The sextant

Answer 6

Named the 60 degree arc instruments designed by tycho brake in the 16th century, has become the common name for all altitude measuring instruments used by navigators. The modern sextant, based on principle of double reflection using mirrors, was Invented in the early 18th century by Isaac Newton, John Hadley and Thomas Godfrey