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A large dome is the most distinctive feature of most planetarium buildings.(Sir Thomas Brisbane Planetarium, Australia)

Inside a planetarium projection hall.(Belgrade Planetarium, Serbia)

Inside the same hall during projection.(Belgrade Planetarium, Serbia)
A planetarium is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation. A dominant feature of most planetariums is the large dome-shaped projection screen onto which scenes of stars, planets and other celestial objects can be made to appear and move realistically to simulate the complex 'motions of the heavens'. The celestial scenes can be created using a wide variety of technologies, for example precision-engineered 'star balls' that combine optical and electro-mechanical technology, slide projector, video and fulldome projector systems, and lasers. Whatever technologies are used, the objective is normally to link them together to provide an accurate relative motion of the sky. Typical systems can be set to display the sky at any point in time, past or present, and often to show the night sky as it would appear from any point of latitude on Earth.
The plural of planetarium can be either planetariums or planetaria.
The term planetarium is sometimes used generically to describe other devices which illustrate the solar system, such as a computer simulation or an orrery.
The term planetarian is used to describe a member of the professional staff of a planetarium.
Planetarium software refers to a software application that renders a three dimensional image of the sky onto a two dimensional computer screen.
Planetariums have become well-nigh ubiquitous, with some privately owned. A rough estimate is that in the United States there is one planetarium per 100,000 population, ranging in size from the Hayden Planetarium's 20-meter dome seating 430 people, to three-meter inflatable portable domes where children sit on the floor. Such portable planetariums serve education programs outside of the permanent installations of museums and science centers.
Contents
1 History
1.1 Early
1.2 After WWII
1.3 Computerized planetariums
2 Planetarium technology
2.1 Domes
2.2 Traditional electromechanical/optical projectors
2.3 Digital projectors
3 Planetarium show content
4 Planetarium software
5 See also
6 References
7 External links
//
History
See also the Timeline of planetariums for specific dates and events in the historical influences on and development of planetariums.
Early

The Franeker planetarium

The Mark I projector installed in the Deutsches Museum in 1923 was the world's first planetarium projector.
Archimedes is attributed with possessing a primitive planetarium device that could predict the movements of the Sun and the Moon and the planets. The discovery of the Antikythera mechanism proved that such devices already existed during antiquity. Johannes Campanus (1220-1296) described a planetarium in his Theorica Planetarum, and included instructions on how to build one. These devices would today usually be referred to as orreries (named for the Earl of Orrery, an Irish peer: an 18th century Earl of Orrery had one built). In fact, many planetariums today have what are called projection orreries, which project onto the dome a Sun with planets (usually limited to Mercury up to Saturn) going around it in something close to their correct relative periods.
The small size of typical 18th century orreries limited their impact, and towards the end of that century a number of educators attempted some larger scale simulations of the heavens. The efforts of Adam Walker (1730-1821) and his sons are noteworthy in their attempts to fuse theatrical illusions with educational aspirations. Walker's Eidouranion was the heart of his public lectures or theatrical presentations. Walker's son describes this "Elaborate Machine" as "twenty feet high, and twenty-seven in diameter: it stands vertically before the spectators, and its globes are so large, that they are distinctly seen in the most distant parts of the Theatre. Every Planet and Satellite seems suspended in space, without any support; performing their annual and diurnal revolutions without any apparent cause". Other lecturers promoted their own devices: R E Lloyd advertised his Dioastrodoxon, or Grand Transparent Orrery, and by 1825 William Kitchener was offering his Ouranologia, which was 42feet (13m) in diameter. These devices most probably sacrificed astronomical accuracy for crowd-pleasing spectacle and sensational and awe-provoking imagery.
The oldest, still working planetarium can be found in the Dutch town Franeker. It was built by Eise Eisinga (1744-1828) in the livingroom of...(and so on)

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