How to make a planetarium

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a 3 meter dome

Ici version française

Abstract: to manufacture a microplanétarium (dome between 1 and 3 meter), it is necessary to project on the aforementioned cupola, an image manufactured by a PC, the software Stellarium and projected with an ordinary videoprojector.

1° images of the realization: dome out of paperboard of 1,2 meters

 

 

2° elements

Stellarium Software: To download urgently if you do not know. Moreover, it is free! a relatively recent and fast graphics board is necessary to use technology OpenGl http://www.stellarium.org/index.html

Videoprojector: in this test, 2 projectors gave satifaction: the model commercial Infocus x1a, and model DIY, standard retrotft (Allinbox philosophy)

Dome: mainly out of paperboard

  • I used the worn paperboards of my removal, a standard hundred grips "bulldog", some cleats. the diameter of the dome, 1.22 meter was selected according to the surface usable of the worn paperboards.
  • the original idea of the structure results from the site: http://www.cccoe.net/stars/
  • the calculation of dimensions of the 2 types of triangles was carried out according to the site http://www.desertdomes.com
  • the joint between 2 triangles is ensured by a band of paperboard folded up of 1 cm broad and 2 grips
  • the dome is fixed at the remainder of the structure by 15 other grips bulldog, broader.
  • the dome directional of 0 with 90° and is maintained by 2 wing nuts
  • the unit is very light, mountable by 1 only person in approximately 30 minutes. Disassembling is much faster (5 minutes)

3° comments and limits of the system

the placement of the public is carried out not as in a traditional planetarium, but rather as for a traditional diaporama, by paying attention not to be interposed on the way of the luminous rays an interesting property of the videoprojector allows the clear manufacture of an image on a dome (depth of field)

the size of the dome of projection is limited by several factors:

If one wants to use the entirety of the dome, the extrèmes left and right edge can be deformed (stars in the shape of features). It is easy to correct this problem by projecting a circle slightly smaller than the dome.

According to the slope of the dome and the presence of a close ceiling, a part of the image can be projected out of the dome; with a projector "house" using an overhead projector, it is easy to remove this nuisance using a mask out of paperboard which one poses on a part of TFT.

4° conclusion

This first test is encouraging. it shows that it is possible for a club or a private individual to manufacture a small planetarium at a reasonable cost. the certainly limited resolution is partly compensated by the wide functionalities which proposes the Stellarium software. If you have already of a PC and a projector, the experiment is not very expensive and deserves to be tried.

 

mail: -yves.lhoumeau-@wanadoo.fr (remove - before and after my name -)

02/2006