What is another word for celestial meridian?
Pronunciation: [səlˈɛstjə͡l mɛɹˈɪdi͡ən] (IPA) 
The celestial meridian refers to an imaginary line that runs from the north to the south celestial poles on the celestial sphere. It is the great circle, which passes through the zenith and the celestial poles, and divides the celestial sphere into two equal hemispheres. Some common synonyms for celestial meridian include celestial equator, celestial prime meridian, and celestial longitude. The celestial equator is a great circle with the same plane as the Earth's equator. The celestial prime meridian is the great circle passing through the north and south poles on the celestial sphere. Celestial longitude refers to the angular distance of a celestial object eastward along the celestial equator from the vernal equinox.
