What is another word for hour circle?
Pronunciation: [ˈa͡ʊ͡ə sˈɜːkə͡l] (IPA) 
Hour circle is a term frequently used in astronomy, referring to the imaginary circle on the celestial sphere that passes through a celestial object and the celestial poles at a given time. Other synonyms for hour circle include hour angle circle, right ascension circle, and meridian circle. The hour angle circle is the celestial equivalent of longitude on the Earth, while the right ascension circle refers to the position of the celestial object measured in hours, minutes, and seconds eastward from the vernal equinox. The meridian circle is an instrument used for measuring the position of celestial objects, but the term can also refer more generally to the celestial meridian.
