Assertion: semicircle | /r/MadeOf | celestial poles
Facets:
Source sentences:
text: An observer's, a semicircle, passes through their zenith and the north and south points of their horizon (see yellow hemi-disk); the observer'sis the semicircle that contains their zenith and both celestial poles.
text: Another way, the meridian is divided into the local meridian, the semicircle that contains the observer's zenith and both celestial poles, and the opposite semicircle, which contains the nadir and both poles.