Planetarium

: planetariums or planetaria) is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation.

[1][2][3] 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 their motion.

[4] In North America, the Hayden Planetarium at the American Museum of Natural History in New York City has the greatest number of seats, at 423.

The ancient Greek polymath Archimedes is attributed with creating a primitive planetarium device that could predict the movements of the Sun and the Moon and the planets.

In 1229, following the conclusion of the Fifth Crusade, Holy Roman Emperor Frederick II of Hohenstaufen brought back a tent with scattered holes representing stars or planets.

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.

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 42 feet (13 m) in diameter.

[8] In 1905 Oskar von Miller (1855–1934) of the Deutsches Museum in Munich commissioned updated versions of a geared orrery and planetarium from M Sendtner, and later worked with Franz Meyer, chief engineer at the Carl Zeiss optical works in Jena, on the largest mechanical planetarium ever constructed, capable of displaying both heliocentric and geocentric motion.

While this was being constructed, von Miller was also working at the Zeiss factory with German astronomer Max Wolf, director of the Landessternwarte Heidelberg-Königstuhl observatory of the University of Heidelberg, on a new and novel design, inspired by Wallace W. Atwood's work at the Chicago Academy of Sciences and by the ideas of Walther Bauersfeld and Rudolf Straubel[9] at Zeiss.

The result was a planetarium design which would generate all the necessary movements of the stars and planets inside the optical projector, and would be mounted centrally in a room, projecting images onto the white surface of a hemisphere.

Meanwhile, the lack of planetarium manufacturers had led to several attempts at construction of unique models, such as one built by the California Academy of Sciences in Golden Gate Park, San Francisco, which operated 1952–2003.

The Korkosz brothers built a large projector for the Boston Museum of Science, which was unique in being the first (and for a very long time only) planetarium to project the planet Uranus.

Goto was particularly successful when the Japanese Ministry of Education put one of their smallest models, the E-3 or E-5 (the numbers refer to the metric diameter of the dome) in every elementary school in Japan.

Unable to pay for this himself, Stern became the head of the planetarium division of Viewlex, a mid-size audio-visual firm on Long Island.

More recently, some planetariums have re-branded themselves as dome theaters, with broader offerings including wide-screen or "wraparound" films, fulldome video, and laser shows that combine music with laser-drawn patterns.

The realism of the viewing experience in a planetarium depends significantly on the dynamic range of the image, i.e., the contrast between dark and light.

Planetaria occasionally include controls such as buttons or joysticks in the arm rests of seats to allow audience feedback that influences the show in real time.

More recently, solid-state LED lighting has become available that significantly decreases power consumption and reduces the maintenance requirement as lamps no longer have to be changed on a regular basis.

This is the largest mechanical planetarium in the world, larger than the Atwood Globe in Chicago (15 feet in diameter) and one third the size of the Hayden.

Some new planetariums now feature a glass floor, which allows spectators to stand near the center of a sphere surrounded by projected images in all directions, giving the impression of floating in outer space.

For example, a small planetarium at AHHAA in Tartu, Estonia features such an installation, with special projectors for images below the feet of the audience, as well as above their heads.

Additional projectors can be added to show twilight around the outside of the screen (complete with city or country scenes) as well as the Milky Way.

These can be of these types:- Despite offering a good viewer experience, traditional star ball projectors suffer several inherent limitations.

An increasing number of planetariums are using digital technology to replace the entire system of interlinked projectors traditionally employed around a star ball to address some of their limitations.

", or shows which pick up on topical issues such as a religious festival (often the Christmas star) linked to the night sky, have been popular.

This new virtual reality capability to travel through the universe provides important educational benefits because it vividly conveys that space has depth, helping audiences to leave behind the ancient misconception that the stars are stuck on the inside of a giant celestial sphere and instead to understand the true layout of the Solar System and beyond.

For example, a planetarium can now 'fly' the audience towards one of the familiar constellations such as Orion, revealing that the stars which appear to make up a co-ordinated shape from an Earth-bound viewpoint are at vastly different distances from Earth and so not connected, except in human imagination and mythology.