celestial equator
–noun Astronomy, Navigation. | the great circle of the celestial sphere, lying in the same plane as the earth's equator. |
Origin: 1870–75
Science Dictionary
celestial equator
A great circle separating the northern and southern hemispheres of the celestial sphere and lying in the same plane as the Earth's equator. The celestial equator is a projection of the Earth's equator outward onto the celestial sphere and is used as the reference point in determining a celestial body's declination.
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The American Heritage® Science Dictionary
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