Abstract: This planetarium is remarkable in that it comprises a sphere (5) consisting of two separate hemisphere (1-2) with diametrically opposed planes facing each other, defining between them a space (e) which can be varied as required, the said hemispheres being joined together by means of connection located at their centre, these being attached to a means (6) located between the two hemispheres, having at least a fixing function in relation to a supporting structure, the said hemispheres being capable, by virtue of their supports, of assuming different positions along the 3 geometrical axes, without any encroachment by the said structure during the projection of the flux onto the vault; the said hemispheres being equipped with means permitting the projection of a luminous flux onto the vault of the planetarium room, and means (11-T) representing certain celestial bodies.