A Planetarium for Every Classroom
Building and Using a Planetarium for Your Classroom Using Inexpensive Materials

Commercially 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 here:

http://shopping.discovery.com/product-28605.html?jzid=40600502-1-0

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.

http://www.mmicorporation.com/catalog/catalog_dwnld.html

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.

http://www.starlab.com/slproj.html

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 oblige.

Projector #2:

This project assumes you have already completed the Projector Cylinder project, and have it on hand.

Your objective here is to build a device that meets the following requirements:

• 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.

-The instructions here will achieve these goals:

1. 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 turntable.

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 cylinder.
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 container black.

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.

Final steps:
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 the curriculum section.

Click here for a printable version

Site counter courtesy of www.digits.com

This project was supported by a County Technology Academy Grant funded by the Dean and Margaret Lesher Foundation in cooperation with the Contra Costa County Office of Education.