In the appts. to display and project the phenomenon of cyclic movements of planets, in a planetarium, at least one of two possible projector assemblies (13) at or in at least one carrier (1 and/or 2) operates on a straight line through the ecliptic pole (EP) and the intersection (M) of three axes (AA;BB;CC) at right angles to each other. At least one of two possible projector assemblies (13) in on a pivot axis at or in at least one carrier (1 and/or 2) on a straight line through the ecliptic pole (EP) and the intersection (M) of three axes (AA;BB;CC) at right angles to each other, for the projector assembly (13) to rotate round the straight line. The intersection (M) of the axes is as close as possible to the centre of the planetarium.
