sextant
Concise Oxford English Dictionary © 2008 Oxford University Press:
sextant /ˈsɛkst(ə)nt/
▶noun an instrument with a graduated arc of 60° and a sighting mechanism, used for measuring the angular distances between objects and especially for taking altitudes in navigation and surveying.
– origin C16 (denoting the sixth part of a circle): from L. sextans, sextant- ‘sixth part’, from sextus ‘sixth’.
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