What is the place where projectors are used to show the night sky?

The place where projectors are used to show the night sky is a planetarium. A planetarium is usually a domed theater in which stars, planets, constellations, and other celestial scenes are projected overhead for education and entertainment.

Traditional planetariums used specialized star projectors, often mechanical machines with lenses and apertures that reproduced the positions and brightness of stars. The first modern planetarium projector, the Zeiss Mark I, was installed at the Deutsches Museum in Munich in 1923. Modern facilities often combine star projectors with digital video, laser systems, and computer-generated views of space.

A planetarium is not the same as an observatory. An observatory uses telescopes to collect real light from astronomical objects, while a planetarium creates an indoor simulation that can show the sky from different places and eras. It can even illustrate events that are difficult to observe directly, such as planetary motion or a journey beyond the Solar System.