# How to use *Celestial-sphere* in a sentence

The line of the equinoxes is the imaginary diameter of the

**celestial sphere**which joins them.The ecliptic itself is the great circle in which this plane meets the

**celestial sphere**.It is also defined, but not with absolute rigour, as the apparent path described by the sun around the

**celestial sphere**as the earth performs its.The conception of the co-ordinates we have defined is facilitated by introducing that of the

**celestial sphere**.Taking as origin the position of an observer, the direction of a heavenly body is defined by the point in which he sees it in the sky; that is to say, on the

**celestial sphere**.AdvertisementThis line, extended upwards, meets the

**celestial sphere**in the zenith.As the earth revolves from west to east the

**celestial sphere**appears to us to revolve in the opposite direction, turning on the line j oining the Celestial Poles as on a pivot.I, the initial line OX is defined as directed toward the vernal equinox, at which point it intersects the

**celestial sphere**.We determine the apparent position of an object near the pole on the

**celestial sphere**at any moment, and again at another moment, twelve hours later, when, by the diurnal motion, it has made half a revolution.The equinoxes are the two points on the

**celestial sphere**where the ecliptic intersects the celestial equator.AdvertisementThe earth's axis projected on to the

**celestial sphere**defines astronomical north.Zones similar to those already drawn out for the

**celestial sphere**were first introduced by the Pythagoreans.In astronomy, we are principally concerned with the orientation of points on a sphere - the so-called

**celestial sphere**- with regard to certain planes and points within the sphere; this subject is treated in the article Astronomy (Spherical).The earth 's axis projected on to the

**celestial sphere**defines astronomical north.