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| the distance traversed by light in one mean solar year, about 5.88 trillion mi. (9.46 trillion km) |
| the small circle of the celestial sphere whose plane is tangent to the earth at the position of the observer |
| meridian circle | |
| —n | |
| an instrument used in astronomy for determining the declination and right ascension of stars. It consists of a telescope attached to a graduated circle | |