The Movement of the Sky as seen from the Equator
This animation shows the movement of the sky as seen from the Equator during the course of one rotation of the Earth, i.e. one sidereal day. The animation shows the whole sky. The thick black line is the horizon. The southern horizon is at the bottom and the northern horizon is at the top. The eastern horizon is on the left and the western to the right. The actual sky is a hemisphere and so there is some distortion as this is projected on the 2D animation. The clock in the lower left-hand corner shows the Local Sidereal Time. Over the course of one day the celestial sphere rotates once around the observer with objects rising in the East and setting in the West.
The grey lines are the RA-Dec grid of the celestial sphere; RA lines are shown every 3 hours ( 0, 3, 6, 9, 12, 15, 18, 21 ), Dec lines are shown every 30° ( −60°, −30°, 0° (celestial equator: red line), +30°, +60°). The green line is the ecliptic ( = the apparent annual path of the Sun on the celestial sphere). The ecliptic plane is tilted 23.5° with respect to the plane of the celestial equator since the Earth’s spin axis is tilted 23.5°. The pole star (Polaris) can be seen at Dec = 90° on the north horizon. The animation starts at a Local Sidereal Time (LST) of 0 hours, i.e. RA = 0h is on the south-north meridian.