in Astronomy, an arch of the horizon, intercepted between the meridian of the place and the vertical circle passing through the centre of the object.

Magnetical Azimuth, an arch of the horizon, intercepted between the vertical circle passing through the centre of any heavenly body and the magnetical meridian.

Azimuth Compass, an instrument for finding either the magnetical azimuth or amplitude of a heavenly object.

Azimuth Circles, called also azimuths or vertical circles, are great circles of the sphere intersecting each other in the zenith and nadir, and cutting the horizon at right angles. On these are reckoned the height of the stars and that of the sun when not in the meridian.