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 comets, 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. Recent developments in planetarium projector technology Since the release of the Evans & Sutherland Digistar in 1983, a single projector with a fish eye lens was able to for the first time show stars from points of view other than Earth's surface, travel through the stars, and accurately show celestial bodies from different times in the past and future. In more recent years, planetaria — or dome theaters — have broadened their offerings to include wide-screen or "wraparound" films, fulldome video, and laser shows that combine music with laser-drawn patterns. The newest generation of planetariums such as Evans & Sutherland's Digistar 6, Global Immersion's Fidelity or Sky-Skan's DigitalSky, offer a fully digital projection system, in which a single 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 sky as visible from points far distant in space and time). While many projection systems maintain their large single or multiple projectors, other systems cater to portable planetariums, like the Emerald planetariums LITE series, at 42lbs to 62lbs, and the Digitalis Education Solutions, Inc Digitarium Iota and Delta 3, at 20.6 and 33.5 lbs, respectively. See also List of planetariums Fulldome Video Planetarium Zeiss projector References External links Planetarium Projector Museum (private collection of retired projectors) 1920s introductions