<P> The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth . This plane of reference bases the equatorial coordinate system . In other words, the celestial equator is an abstract projection of the terrestrial equator into outer space . As a result of the planet's axial tilt, the celestial equator is currently inclined by about 23.44 ° with respect to the ecliptic (the plane of earth's orbit). </P> <P> An observer standing on Earth's equator visualizes the celestial equator as a semicircle passing through the zenith, the point directly overhead . As the observer moves north (or south), the celestial equator tilts towards the opposite horizon . The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus, the ends of the semicircle always intersect the horizon due east and due west, regardless of the observer's position on Earth . (At the poles, the celestial equator coincides with the astronomical horizon .) At all latitudes, the celestial equator is a uniform arc or circle because the observer is only finitely far from the plane of the celestial equator, but infinitely far from the celestial equator itself . </P> <P> Astronomical objects near the celestial equator appear above the horizon from most places on earth, but they culminate (reach the meridian) highest near the equator . The celestial equator currently passes through these constellations: </P> <Table> <Tr> <Td> <Ul> <Li> Pisces (contains the first point of Aries above its southern border) </Li> <Li> Cetus </Li> <Li> Taurus </Li> <Li> Eridanus </Li> <Li> Orion </Li> </Ul> </Td> <Td> <Ul> <Li> Monoceros </Li> <Li> Canis Minor </Li> <Li> Hydra </Li> <Li> Sextans </Li> <Li> Leo </Li> </Ul> </Td> <Td> <Ul> <Li> Virgo (contains the first point of Libra) </Li> <Li> Serpens (caput) </Li> <Li> Ophiuchus </Li> <Li> Serpens (cauda) </Li> <Li> Aquila </Li> <Li> Aquarius </Li> </Ul> </Td> </Tr> </Table>

When do the celestial equator and ecliptic coincide