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

Building a projector is essential to using the planetarium dome to teach a number of lessons including the diurnal (daily) motion of the sun and stars, the dependency of the sky’s appearance on latitude, and more.

Fortunately it is relatively easy to build a projector. High quality projectors are also available from sources such as MMI Corporation and Learning Technologies. See the projector page for more options. The projector we will describe is not as good as these projectors, but it will be better than the toy projectors you find in toy stores, intended for use on a darkened bedroom ceiling.

With some effort and advanced skills it would be possible to build an extremely advanced projector. Some of the considerations needed for such a project will be discussed along the way, but only the basic projector will be fully described.

Recently the cost of digital projectors are falling to the point where you may be able to afford one. If so, several programs such as Starry Night, Celestia, The Sky, Redshift, Voyager, and others could provide a digital image for your dome. For a more complete listing, visit AstronomyTeacher.com, click on Links, and then click on Software.

Purpose: Build an adjustable projector useful for showing the positions of stars.

NOTE: In practice, we have found that the laser printing method described below does not yield black enough black areas on the transparency to block the light 100%. Screen printing might, but we haven't tried it. Our most successful design was done by poking holes in a cylinder which was made by covering a Mercator projection star chart

(Available from Sky publishing at this link: (http://www.shopatsky.com/index.asp?PageAction=VIEWCATS&Category=115 , order SC 001 and SC 002 )

with black contact paper. An awl was used to make the holes.

Downloadable maps are available from Paul Bourke's web site: http://local.wasp.uwa.edu.au/~pbourke/modelling_rendering/starfield/cyl.html

Another design involving drilling holes in a spherical projector, is described on the projector page. The instructions below are still here, presented as a way for you to experiment with different designs.

Materials:

Optional: lightly tinted transparent plastic sheets such as from an envelope window.

1. At the following links you will find two star charts one for the cylinder walls the other for the lid.

Click on the file name below to access files:

Please note these are proof-of-concept images and are not the finished version.

Cylinder Wall

Cylinder Lid

These are still under revision and someday will include several variations.

You need to print these out on transparencies using a good quality laser printer. Consult your printer manual to find out how to properly load the laser transparencies into the printer. It may also work (but not as well) to print the masters out on paper and use a photocopier to make the masters. In any case, make sure you use transparencies designed for the printer or copier you are using. Thermal transparencies, for example, will melt onto the print cylinder of a copier and cause expensive repairs to be needed.

2. Identify which side of the transparency is the “inside” and which is the “outside.” The inside of the transparency has letters written normally. The outside of the transparency will have the letters written backward.

3. Carefully trim the clear borders from each transparency, except for the bottom. Cut slowly and precisely.

4. The Wall gets assembled into a cylinder and the cap fits on top.

5. Use very small pieces of electrical tape to secure the cylinder lid to the cylinder. Using very small and narrow pieces of electrical tape, work your way around the cylinder lid, trying not to cover any bright stars on the charts as you go.

8. Snip notches in the bottom of the clear section remaining on the cylinder maps, so that the resulting tabs can be folded outward. These will be used to secure the cylinder to the projector with velcro, so you can put the loop pieces of velcro on the inside (bottom) of the clear tabs you have made.

9. Use a permanent maker to eliminate any scratches, including the alignment mark on the round chart. Your projection cylinder is now complete.

Tips: Use a laser printer set to maximum darkness to make the cylinder.

Consider printing a negative version of the cylinder with clear walls and use dark lines with clear background.

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.