octant

1. The eighth part of a circle; an arc of 45 degrees.

2. The aspect of two planets that are 45°, or one-eighth of a circle, apart.

3. The eighth part of a disc; a sector of 45 degrees; half a quadrant; one of eight divisions of a sphere by three orthogonal planes.

4. An instrument for measuring angles, particularly of elevation.

   окта́нтoktánt

   a measuring instrument for measuring angles to a celestial body; similar to a sextant but with 45 degree calibration

regular