| The heart of the Sky
Theater of the planetarium is the star projector. When the planetarium
was originally constructed, a Spitz Intermediate Space Transit Planetarium
(ISTP) projector was installed. The Spitz ISTP projector was an optical-mechanical
system that was one of the most advanced planetarium projectors of
its time. The Spitz ISTP incorporated miniaturized electronics and
components and therefore weighed less (under 1,000 pounds) than most
projectors of its time. This reduction in weight and inertia allowed
the projector to move in ways other projectors could not. In fact,
the projector was able to move in three axes of motion, thereby allowing
the planetarium to simulate the movement of the stars through the
night, but also the movement of a vehicle in space.
|| The optical-mechanical
nature of the Spitz ISTP meant that it projected the night sky onto
the dome by the use of lights and lenses. The projector consisted
of a Star Hemisphere at either end of the projector. Each Star Hemisphere
had charts of the night sky mapped on them. Light was emitted from
the hemispheres through over 4000 small holes that represented the
dimmer stars, or over 200 larger ones which contained lenses and filters,
to represent the brighter stars and objects in the night sky. The
light that was emitted came from high pressure Xenon gas arc lamps
placed within the hemispheres.
| The projector also contained Instrument
Analogs which allowed it to simulate the motions of objects in the
solar system. The Instrument Analogs duplicated the motions of the
five observable naked eye planets as they traveled through the background
stars. The Spitz ISTP also would allow for the a simulation of the
Moon and the Sun through the sky.
| The projector was
operated from a Control Console found at the back of the theater.
From this area the operator could adjust show volume and cove lights
along with adjust the motions of the stars, planets, Sun, and Moon.
| The Spitz ISTP projector installed
in the Abrams Planetarium was only one of less than a dozen ever produced,
in fact it was the prototype of the model. Although advanced for its
time, the projector eventually began to show its age as technological
knowledge increased. In 1993 the Spitz ISTP was retired and was removed
from the Sky Theater, to be replaced
by the Digistar, a digital star
projector. Although it is no longer used, its memory still persists
and many patrons wonder what ever became of the star projector that
excited their interests in astronomy when they were children.