Planetarium projector
Encyclopedia
A planetarium projector is a device used to project images of celestial objects onto the dome in a planetarium
.
The first modern planetarium projectors were designed and built by the Carl Zeiss Jena
company in Germany
between 1923 and 1925, and have since grown more complex. Smaller projectors include a set of fixed stars, Sun, Moon, and planets, and various nebula
e. Larger machines also include comet
s and a far greater selection of stars. 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
. Still others add coordinate lines and constellation
s, photographic slides, laser
displays, and other images. The OMNIMAX
movie
system (now known as IMAX Dome) was originally designed to operate on planetarium screens.
A good example of a "typical" planetarium projector of the 1960s was the Universal Projection Planetarium type 23/6, made by VEB
Carl Zeiss Jena
in what was then East Germany. The planetarium projector was a 13 feet (4 m)-long dumbbell-shaped object, with 29 inches (736.6 mm)-diameter spheres attached at each end representing the night sky for the northern and southern hemispheres. Connecting the two spheres was a framework that held nearly 150 individual projectors, including those dedicated to the planets, the Sun, and specific stars.
Each globe held representations of almost 4,500 stars per hemisphere. The "stars" were created by tiny holes that were punched into copper foil, ranging from 0.023 to 0.452 mm in size, the larger holes letting more light get through and thereby creating brighter star images. Two glass plates held this foil between them to create what was called a "star field plate". Each globe was illuminated using a 1,500-watt lamp that was located in its center. A number of aspherical condenser lenses were placed within each globe to focus the light onto the plates. Twenty-three of the most prominent stars had their own projectors, designed to project a small disk instead of pinpoint of light, and were also colored: Betelgeuse
and Antares
would appear reddish, Rigel
and Spica
would each have a blue tinge. An image of the Milky Way
was created by using drum-type projectors that were studded with unfocused pinprick-sized holes based on photographic images of our galaxy. Specific projectors could imitate the light changes of such variable stars as Algol or Omicron Ceti, and other projectors could produce images of the constellations, of specific historical comet
s, compass points and other astronomical phenomena. When a particular star or planet dipped below the artificial horizon
, a gravity-based mercury
-filled shutter would be activated, blocking out the light.
, and laser shows that combine music with laser-drawn patterns. The newest generation of planetariums such as Evans & Sutherland
's Digistar 3
, Global Immersion's Fidelity
or Sky-Skan's DigitalSky, offer a fully digital
projection system, in which a single large projector with a fish eye lens, or a system of digital video or laser video projectors around the edge of the dome, are used to create any scene provided to it from a computer. This gives the operator tremendous flexibility in showing not only the modern night sky as visible from Earth
, but any other image they wish (including the night sky as visible from points far distant in space and time).
Planetarium
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...
.
The first modern planetarium projectors were designed and built by the Carl Zeiss Jena
Carl Zeiss Jena
Carl Zeiss Jena may refer to:* FC Carl Zeiss Jena, a German football club based in Jena, Thuringia* Carl Zeiss Jena , a German optics company based in Jena, Thuringia...
company in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
between 1923 and 1925, and have since grown more complex. Smaller projectors include a set of fixed stars, Sun, Moon, and planets, and various nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
e. Larger machines also include comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s and a far greater selection of stars. 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
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
. Still others add coordinate lines and constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
s, photographic slides, laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
displays, and other images. The OMNIMAX
IMAX
IMAX is a motion picture film format and a set of proprietary cinema projection standards created by the Canadian company IMAX Corporation. IMAX has the capacity to record and display images of far greater size and resolution than conventional film systems...
movie
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
system (now known as IMAX Dome) was originally designed to operate on planetarium screens.
1960s
Volkseigener Betrieb
The Volkseigener Betrieb was the legal form of industrial enterprise in East Germany...
Carl Zeiss Jena
Carl Zeiss Jena
Carl Zeiss Jena may refer to:* FC Carl Zeiss Jena, a German football club based in Jena, Thuringia* Carl Zeiss Jena , a German optics company based in Jena, Thuringia...
in what was then East Germany. The planetarium projector was a 13 feet (4 m)-long dumbbell-shaped object, with 29 inches (736.6 mm)-diameter spheres attached at each end representing the night sky for the northern and southern hemispheres. Connecting the two spheres was a framework that held nearly 150 individual projectors, including those dedicated to the planets, the Sun, and specific stars.
Each globe held representations of almost 4,500 stars per hemisphere. The "stars" were created by tiny holes that were punched into copper foil, ranging from 0.023 to 0.452 mm in size, the larger holes letting more light get through and thereby creating brighter star images. Two glass plates held this foil between them to create what was called a "star field plate". Each globe was illuminated using a 1,500-watt lamp that was located in its center. A number of aspherical condenser lenses were placed within each globe to focus the light onto the plates. Twenty-three of the most prominent stars had their own projectors, designed to project a small disk instead of pinpoint of light, and were also colored: Betelgeuse
Betelgeuse
Betelgeuse, also known by its Bayer designation Alpha Orionis , is the eighth brightest star in the night sky and second brightest star in the constellation of Orion, outshining its neighbour Rigel only rarely...
and Antares
Antares
Antares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky . Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic...
would appear reddish, Rigel
Rigel
Rigel is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0.18...
and Spica
Spica
Spica is the brightest star in the constellation Virgo, and the 15th brightest star in the nighttime sky. It is 260 light years distant from Earth...
would each have a blue tinge. An image of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
was created by using drum-type projectors that were studded with unfocused pinprick-sized holes based on photographic images of our galaxy. Specific projectors could imitate the light changes of such variable stars as Algol or Omicron Ceti, and other projectors could produce images of the constellations, of specific historical comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s, compass points and other astronomical phenomena. When a particular star or planet dipped below the artificial horizon
Horizon
The horizon is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. At many locations, the true horizon is obscured by trees, buildings, mountains, etc., and the resulting...
, a gravity-based mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
-filled shutter would be activated, blocking out the light.
Recent developments in planetarium projector technology
In recent years, planetariums — or dome theaters — have broadened their offerings to include wide-screen or "wraparound" films, fulldome videoFulldome
Fulldome refers to immersive dome-based video projection environments. The dome, horizontal or tilted, is filled with real-time or pre-rendered computer animations, live capture images, or composited environments....
, and laser shows that combine music with laser-drawn patterns. The newest generation of planetariums such as Evans & Sutherland
Evans & Sutherland
Evans & Sutherland is a computer firm involved in the computer graphics field. Their products are used primarily by the military and large industrial firms for training and simulation, and in digital projection environments like planetariums.-History:...
's Digistar 3
Digistar 3
Digistar 3 is a dome-based projection technology created by Evans & Sutherland - to offer audiences immersive entertainment and education experiences that integrate fulldome video, real time 3D computer graphics, and a digital planetarium facility...
, Global Immersion's Fidelity
Fidelity
"Fidelity" is the quality of being faithful or loyal. Its original meaning regarded duty to a lord or a king, in a broader sense than the related concept of fealty. Both derive from the Latin word fidēlis, meaning "faithful or loyal"....
or Sky-Skan's DigitalSky, offer a fully digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
projection system, in which a single large projector with a fish eye lens, or a system of digital video or laser video projectors around the edge of the dome, are used to create any scene provided to it from a computer. This gives the operator tremendous flexibility in showing not only the modern night sky as visible from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, but any other image they wish (including the night sky as visible from points far distant in space and time).