Planetarium. Night sky projected onto the dome of a planetarium. The projection equipment is seen at centre right. This scene shows the night sky just before sunrise (red glow on horizon). An airplane silhouette is seen at lower left. As well as the stars, the Moon and some of the planets are also seen. This is the planetarium of the Astronomical Observatory of Capodimonte (OAC), Naples, Italy. The main projector is a 40-centimetre-diameter hollow sphere lit from the inside, with 3200 holes to project images of stars down to fifth magnitude brightness. The semi-spherical dome (5.2 metres across) is rotated to simulate Earth's rotation. The projector sphere is rotated to change position on the Earth. This planetarium seats 20 people.