By Francis Graham Asst Prof. Physics, Kent State University


Published in the Newsletter of the Home Planetarium Association, Vol. 1 No.  1



    Planetaria are extremely expensive if purchased commercially. The only planetaria of great value and accuracy are the renowned Zeiss and Spitz planetaria, each of which costs in excess of $10,000.  These expensive planetaria often have limited instructional objectives and remain in affluent "WASP" schools as prestige items.  While some less-than-affluent schools have taken the surplus planetarium purchase route (1) , obviously, when the value of the planetarium in a limited funded program is in doubt, it becomes wise to build a small experimental model as cheaply and as quickly as possible, and evaluate it.

   The policy was selected by the Science Department at Tri-City OIC in 1975 and implemented. The Tripoli Federation provided the funds of $10 required to purchase some items for constructing the planetarium.

   The first germs of a home-made planetarium came from a vivid description of the Stephen Smith planetarium in Prescott, Arizona (2). Mr. Smith's planetarium is a cylindrical 20-inch diameter machine showing all stars to magnitude 5.5.  This planetarium is extremely inexpensive, costing less than $100; however, a great deal of labor time is required that was not immediately available here.

   A second design and model was presented as an exhibit at the 1975 Middle East Regional Astronomical League convention.  The exhibit carried no label, and its designer is not known.  The planetarium featured a large spherical projector on a wooden frame, with Milky Way projection and a motorized mount. In addition, available options such as comets were available.

   Encouraged by such a less involved design, the author made a preliminary sketch of a portable planetarium and three revisions, until a fourth model number 4 (3) seemed a feasible design utilizing a stand similar to the Mazur 6-inch telescope stand. Clock driven, the model 4 design has a bob-weighted artificial horizon.  These concepts were discussed with Professor John Townsend of the University of Pittsburgh, who made suggestions as to its applicability to the Alternative Curriculum Program for Freshmen there.  It was suggested that the students construct the planetarium, since modeling is one of the best ways to learn fundamentals.

   Unfortunately, although Professor Townsend's reply was immensely encouraging (4) the astronomy workshop could not be organized in the Fall of 1975 due to a low program enrollment.

  The ideas remained however and were utilized experimentally at the Tri-CIty O.I.C., a community-based organization with adult education programs.

  The planetarium envisioned for Tri-City OIC was to follow along the same lines as Model 4, but less elaborate and less experimental. The goals of the Tri-City OIC planetarium were:


   (1) to test the techniques and tooling required for Model 4;

   (2) to be absolutely of zero expense to Tri-City OIC

   (3) to evaluate and develop the planetarium for curriculum use.

   (4) to provide itself as a basis for classroom discussion and        de-mystify the planetarium in the experience of the        students.


    The demystifying aspect has been shown to be of a high value in the popular appreciation of large civic planetaria(5).

   The planetarium was to consist of holes drilled into an old world globe at the appropriate places converted from right ascension and declination into longitude and latitude. World globes purchased new are expensive, and often are made of plastic nowadays instead of aluminum. It was hoped therefore to purchase a world globe used at a flea market or some other used-goods outlet. Three weekly checks of the large Greater Valley Sunday market failed to demonstrate a world globe; therefore an alternate source was adopted.

   Leonard's Salvage of Braddock was selling Replogle Lunar globes at $2 each.  The author purchased one quickly, using funds provided by the Tripoli Federation.  On two consecutive weekends, the author marked the globe and drilled the stars accordingly.  A 1/16-inch diameter (0.1587 cm.) drill bit was used for the stars.  Smaller stars were created by pin-holing a scrap of aluminum foil and expoxying the scrap over the 1/16-inch drilled hole.  The Pleiades star cluster was created by drilling a 1/4-inch (0.635 cm.) hole and then placing over it a scrap of aluminum foil upon which had been pin-holed the cluster.

   Initially, it had been planned to use a high-wattage AC Light.  However, AC lamps are not available with small filaments. Large filaments could not be used because the star holes created a camera obscura effect and projected W-shaped filaments instead of nice, round stars.  Therefore, a completely inertial battery-operated 3.7-watt light was selected.  This had the disadvantage of requiring the operator to open the globe to change batteries and to open the circuit and to close it.

   Only the brighter stars of the Northern and southern hemispheres were selected, with some lesser stars to complete traditional constellation geometries. These stars are wholly representative of the stars seen in the type of sky presented in the McKeesport area, immersed in the illegally-discharging Clairton Coke Works of the United States Steel Corporation (6, 7).  Thus, it successfully communicates constellation recognition by bright star identification without the fiction of an Arizona sky (8).

    The 100 brightest stars were chosen as well as those needed to complete constellations. Star positions were obtained from the already-compiled Tripoli Star Catalog and then were checked against a 12-inch (30.48 cm.) Apollo celestial globe. All star positions are accurate to 0.4 cm. which is not extremely accurate for a star projector.

   The initial dome was constructed from white tissue paper and wooden screen-door slats; it was four meters in diameter, approximately hemispherical and could be raised to the ceiling or lowered by a ceiling hook-and-rope.

   The Planetarium was initially tested November 13, 1975 at 7 p.m.(10). Star images were quite visible, but the room had to be completely darkened.  It was discovered that light entering over a partition-type wall was sufficient to destroy the effect.  The auto mechanics instructor, Frederick Krinks, was present at the test.

   It was obvious that light leaks would have to be stopped and a stronger light source was required.  Also needed was additional support for the wood frame structurally. 

   Over the period January 1-11, 1976, the dome was revamped and black paper was placed outside of the dome.   Thus it was possible to continue the experiment on use of a handcrafted planetarium in the classroom.

   In addition, the dome tended to tatter from heat from a nearby heater.  Therefore, we relocated the dome away from the heater.

   A 12-watt 12-volt light source was installed and the power source was made external.  Plastic tape was added to the joints of the bracing to prevent accidental eye injury.

   Following the extensive revamping, the experiment continued with the use of two new times.

   On January 12, 1976, operational use of the Planetarium was made for the first time. Adult Basic Education Group A (Becky Neetlestone et al) was exposed (11) to the planetarium.  This was a unit on the stars and celestial motions, required in their curriculum. As a tool for teaching this, the planetarium can't be surpassed. Comprehension and grasp of the meaning of the stars rising and setting diurnally as well as the apparent motion of the sun through the Zodiac constellations was quick using this tool (12). An examination was given January 15, 1976 to this group to test their knowledge gained from this lesson.  All of the students scored above 60% correct answers.

   On January 13 we tried something different.  In this group, C, fish were to be studied. It was hoped to use this planetarium to enhance appreciation by projecting multiple images of undersea life on the screen.  This experiment failed when heat began to build up under the dome from the projection apparatus.  Dr. Cheryl Campbell was present at this experiment and disagreed with using the planetarium this way.

   Tri-City OIC moved out of the 136 Sixth Street, McKeesport, building shortly thereafter and there was not room in the new building for the activity of a planetarium.  The first planetarium in McKeesport was dismantled in September, 1976. 

   The first planetarium in McKeesport was only possible because of excess space and high ceilings at the 136 Sixth Street building. With more limited space, the planetarium could not be re-continued.  It was however the first one in any of the nationally based OICs (Opportunities Industrialization Centers).





1. Mergler, Robert "The Planetarium in the Junior High School Science Curriculum” School Science and Mathematics 75, 7 p. 591-593.

2. Smith, Steven B., "An Inexpensive Home-Built Planetarium Projector" Sky and Telescope 48 1 p. 27-29.

3. Graham, F.G., "Planetarium Design No. 4" unpublished, Tripoli Federation Records, Vol. XLVIII, June 14, 1975.

4. Townsend, John R., personal communication.

5. Ridkey, Robert W, "The Mystique Effect of the Planetarium" School Science and Mathematics 75, 6 pp505-508

6. Graham, FG "Teaching Astronomy in a Polluted City" submitted for publication.

7. Klack, Frank et al "Art XVII: Smoke and Air Pollution Control" Alleg. Co. Dept. of Health, Sept. 1969.

8. Reed, George R., "The Planetarium vs. the Classroom" School Science and Mathematics 73, 6 p. 555.

9. Graham, F.G. and Graham, C.B. The Tripoli Star Catalog, unpublished.

10. Graham, F.G. "Toward an Inexpensive Classroom Planetarium" unpublished, Tripoli Federation Records, LII, Nov 13, 1975.

11. Graham, F.G. "Progress Report on the Inexpensive Classroom Planetarium System" ibid, Vol. LIII, Jan 13, 1976.

12. Letsch, Heinz Captured Stars Fisher Verlag, Jena: 1959.