Definition:Celestial Horizon

Definition
The celestial horizon is the great circle on the celestial sphere whose plane is perpendicular to the line from the zenith to the observer.

Thus the celestial horizon is the edge of the visible part of the celestial sphere.

The rest of it is hidden by Earth itself.

Also known as
The celestial horizon is also known just as the horizon, and as such is used in common parlance to mean as far as can be seen, figuratively as well as literally.

Also see

 * Definition:Horizontal


 * Definition:Visible Hemisphere