Visitors, please note that the RMSC Museum and Strasenburgh Planetarium will be CLOSED for deep cleaning from Monday, Sept. 18 through Sunday, Sept. 24.

Cumming Nature Center will remain OPEN.

The Star Projector

The planetarium star projector accurately shows the sun, moon, naked-eye planets, and 8,900 stars as they would appear to the naked eye under perfect viewing conditions from any point on Earth on any date. The beauty and accuracy of the planetarium sky is in perfect harmony with the Strasenburgh Planetarium's dedicated purpose: to foster a fuller understanding and appreciation of the order and majesty of the universe.

The star projector shows only the objects visible to the naked eye in Earth’s sky. All the other imagery in a planetarium star show comes from hundreds of auxiliary projectors, many of which were invented and built in the Strasenburgh shops. Most of those projectors can be controlled by a computer.

Here are some frequently asked questions about the Planetarium star projector:

Who made Rochester's star projector?

The firm of Carl Zeiss, Oberkochen, Germany

Why do we sometimes call the projector “Carl”?

Because it was made by the Carl Zeiss company.

Is Zeiss the only company in the world that makes planetarium projectors?

No. Several other firms also manufacture various types of planetarium star projectors. Here, in alphabetical order, are some leading manufacturers of planetarium projectors for large theaters (any omissions are inadvertent):

  • Evans & Sutherland (Computer Graphics Co)
  • GOTO (Planetarium)
  • Konica Minolta (Planetarium)
  • R.S.A. Cosmos (Planetarium)
  • Sky-Skan (National Air & Space Museum)
  • Spitz (Planetarium)
  • Zeiss (Planetarium)

When was the Strasenburgh Planetarium star projector installed?

In 1968, when the Planetarium opened. The projector has been in continuous service ever since.

How much did it cost?

$240,234 (in 1968 dollars).

How does it make the stars?

The Zeiss instrument has 32 star field projectors, each covering a particular area in the sky. Inside each star field projector, there is a metal plate with tiny holes. Light from the star lamp shines through the holes, passes through a focusing lens, and strikes the dome, making small dots of light representing the stars. The 15 brightest stars have their own individual projectors, attached at various places on the main structure.

Is the star projector a robot?

The word “robot” usually means a mechanical device that can be programmed to do a job automatically. The Strasenburgh Planetarium star projector is not automatic; it is always under the direct control of the show operator, stationed at the control console at the side of the theater. Knobs on the console turn the sun, moon, planets, and stars on and off, and control the various motions of the instrument. Since the gears that move the sun, moon, and planet projectors are designed to move in the same speed ratios as the actual heavenly bodies, it might be more appropriate to call the instrument an analog computer.


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