celestial horizon

noun

Astronomy.

1. horizon2b

celestial horizon

noun

1. See horizon

celestial horizon

1. A great circle on the celestial sphere having a plane that passes through the center of the Earth at a right angle to the line formed by an observer's zenith and nadir. The celestial horizon divides the celestial sphere into two equal hemispheres based on the observer's location, with one hemisphere representing the half of the sky visible to the observer at that location and the other representing the half that is hidden from the observer below the Earth's horizon. The celestial horizon is used as the reference point in determining a celestial body's altitude.

2. Also called rational horizon

3. Compare sensible horizon

Word History and Origins

Origin of celestial horizon¹

First recorded in 1895–1900