octant

[ ok-tuhnt ]

Phonetic (Standard)IPA

noun

the eighth part of a circle.
Mathematics. any of the eight parts into which three mutually perpendicular planes divide space.
an instrument having an arc of 24°, used by navigators for measuring angles up to 90°.
the position of one heavenly body when 45° distant from another.
Octant, Astronomy. the constellation Octans.

octant

/ ˈɒktənt /

maths
1. any of the eight parts into which the three planes containing the Cartesian coordinate axes divide space
2. an eighth part of a circle
astronomy the position of a celestial body when it is at an angular distance of 45° from another body
an instrument used for measuring angles, similar to a sextant but having a graduated arc of 45°

Origin of octant¹

First recorded in 1680–90; from Latin octant- (stem of octāns ); Octans

Origin of octant¹

C17: from Latin octans half quadrant, from octo eight

Thus fig. 59 conveniently represents an octant of the wave surface, which cuts each coordinate plane in a circle and an ellipse.

It is the sextant or some member of the sextant family - such as the quadrant, octant, etc.

A third staff (or an octant) was fixed at the end of the horizon-staff, and upon it the angle observed could be read off.

The third plane will lie horizontal or equatorial, and will divide each of these quarters into an upper and lower octant.

Excluded, of course, are those instruments normally made of wood, such as the octant and the mariners quadrant.

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