available star projectors:
A variety of small planetarium projectors are available commercially.
Some of these are excellent for the small planetarium. Two examples
can be found below.
The cheapest option is the Discovery channel projector displayed
If the link doesn't work search for "Discovery Star Theatre Home
Planetarium." You get a negative projected image, but it will provide
more light inside the dome for the little kiddies and it's cheap
(approx. $30.00 US).
MMI Corporation sells a variety of small projectors including a
self-contained setup which includes a 10-foot diameter dome. We think
our dome is better (and larger) but the projector might be worth
looking at. Click on the link and download the "Planetarium" catalog
for more information.
STARLAB planetariums (the inflatable kind you may have seen) also
include a projector. Learning Technologies has just come out with
a new high-tech version as well. They are pricey, but the are the
standard for small portable planetariums.
Our Homemade Planetarium Projector#1:
Students Josh Santos, Robert Johnson, and Barry Parker completed
this fixed projector as a project in 2004. It consists of a light
bulb held in the center of a plastic sphere, through which they drilled
holes in the patterns of the stars. We don't have a writeup yet but
if you really want more details, drop us a note and we'll try to
This project assumes you have already completed the Projector
and have it on hand.
Your objective here is to build a device that meets the following
- A small, bright light is suspended in the exact geometric center
of the Projector Cylinder.
The bulb should be replaceable in case it blows.
The bulb should be as small as possible.
The entire apparatus should be rotatable along the long axis of the cylinder.
The entire apparatus should be able to tilt to different levels
between 0 and about 45 degrees.
Light from the bulb should not illuminate the bottom of the cylinder,
no matter what the orientation.
here will achieve these goals:
|small bright light
|6V latern batteries
||Coat hanger wire
Cut a piece of dowel rod about a centimeter shorter than half of
the projector cylinder. Mount the light bulb socket to the top of
this rod by using glue, screws or any other convenient means including
duct tape if necessary.
2. Connect wires to the bulb socket. The wires
need to be longer than the dowel rod by several inches.
3. Connect the wires to the switch (if used)
or directly to the battery to test the light bulb function. 6V
lantern batteries last a long time and provide plenty of power.
If the bulb is rated at 6V, the light should be sufficiently
bright. If you have a switch, extend the wires outside the radius
of the projector cylinder so you can switch the light on and
off without removing the cylinder.
4. Attach the battery and light bulb assembly
to the lazy susan. One method is to run a screw through the bottom
of the turntable to the rod; if the enter of the turntable is
hollow, then you may need to duct tape the battery assembly to
the turntable or mount a piece of thin plywood on top of the
5. Next, if you want your projector to block off
stars not visible because they are below the horizon, build this
device using a small plastic container and coat hanger wire.
You need a container larger than the light bulb and smaller than the projector
Cut a slot out of the
container which starts in the bottom, goes out to the edge, and goes most of
the way up the side. The slot should be wider than the
rod and wire assembly. Pierce two holes on the sides of the container on either
side of the container, near the top.
Note: The small holes should be centered
on the sides, but the bottom slot should extend past the middle enough
to clear the central dowel rod.
6. Paint or color the interior surface of the
7. Bend a piece of coat hanger wire so that it
acts as a support for the box. Begin by making an arm support for
one side, then wrap the coat hanger around the dowel below the level
of the box. Bring the wire up to the other side and use it to support
the other side of the box. The top edge of the box should be level
with the center of the light bulb. Secure the coat hanger to the
dowel rod with duct tape.
8. Test fit the projector cylinder by putting it
on top of the light bulb assembly. If everything fits, you should
be able to turn on the light bulb and rotate the projector cylinder
360 degrees without catching any wires, etc.
9. The last step for the basic projector is to
mount the turntable bottom on a piece of plywood, and then attach
this via a hinge to a base. You can then tilt the entire assembly
and brace it with books or blocks to simulate different latitudes.
10. Some extra velcro loops or pieces of thick
felt underneath the turntable should keep it from rotating freely.
If you don’t do this, the weight of the battery will cause
it to swing to the bottom.
11. When using the projector in the dome, the projector
should be mounted at the center of the sphere, at the height of the
top of the base ring.
12. Keep a spare bulb handy...and a flashlight
for disciplinary problems ;-).
For more ideas on how to use the projector and dome together, see
Click here for
a printable version