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An instrument whose magnetized metal
needle aligns itself with the magnetic fields of the earth. This causes
one end of the needle to point north. Mariners used this information
to navigate the ship. The Chinese are said to have invented the first
compass over 2000 years ago. |
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A representation of a region of the earth or heavens.
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This tool was once used to determine the altitude
of the sun or other celestial bodies. |
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An early sixteenth-century instrument for measuring
the altitude of a heavenly body. It consists of a square shaft and
a sliding cross-piece set at right angles to the shaft. The shaft
end is held at the observer's eye and the cross-piece positioned to
line up with the sun and the horizon. The cross-piece marks a point
on the shaft that is referred to in a table of degrees and minutes.
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The quadrant
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An early instrument for measuring altitude of celestial
bodies, consisting of a 90° graduated arc with a movable radius
for measuring angles. |
The sextant
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A navigational instrument which replaced the astrolabe
and was used for measuring the angle between the horizon and the sun
or a star in order to find out the latitude (of a ship) |