octant
noun
- measuring instrument used primarily in navigation; type of reflecting instrument
Wiktionary
noun
Etymology: From Latin octāns. Doublet of Octans.
- The eighth part of a circle; an arc of 45 degrees.
- The aspect of two planets that are 45°, or one-eighth of a circle, apart.
- The eighth part of a disc; a sector of 45 degrees; half a quadrant.
- An instrument for measuring angles, particularly of elevation.