Planetarium

A planetarium has a planet projection system comprising: a rotatable stage positioned concentrically with a precession axis of a fixed star projection globe and performing an X-axis motion; and a sleeve-type planet projector positioned at an eccentric position with respect to an X axis on the rotatable stage and performing a Y-axis motion for allowing a projection direction to vary upward and downward in relation to the rotatable stage. The X-axis and Y-axis motions are controlled on the basis of values calculated by a planet-movement operation unit receiving date and time data, to project the movement of planets.