in which city was the world's first planetarium projector installed in 1923
Zeiss projector The first Zeiss Mark I projector (the first planetarium projector in the world) was installed in the Deutsches Museum in Munich in August, 1923.[2] It possessed a distinctive appearance, with a single sphere of projection lenses supported above a large, angled "planet cage". Marks II through VI were similar in appearance, using two spheres of star projectors separated along a central axis that contained projectors for the planets. Beginning with Mark VII, the central axis was eliminated and the two spheres were merged into a single, egg-shaped projection unit.