Horizon

The circle round the Earth that separates the visible and the invisible hemispheres. The terms sensible, visible or physical horizon are often employed, indicating the line which terminates our vision, where the celestial bodies appear and disappear. The astronomical horizon, termed the rational horizon, is obtained by supposing a line drawn from the Earth's center parallel with the horizon. Astrologically, the eastern horizon is the degree rising in the east, and the Sign then appearing is the Rising Sign.