<P> A Zeiss projector is one of a line of planetarium projectors manufactured by the Carl Zeiss Company . </P> <P> The first modern planetarium projectors were designed and built in 1924 by the Zeiss Works of Jena, Germany in 1924 . Zeiss projectors are designed to sit in the middle of a dark, dome - covered room and project an accurate image of the stars and other astronomical objects on the dome . They are generally large, complicated, and imposing machines . </P> <P> The first Zeiss Mark I projector (the first planetarium projector in the world) was installed in the Deutsches Museum in Munich in August, 1923 . 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 . </P> <P> The Mark I was created in 1923--1924 and was the world's first modern planetarium projector . The Mark II was developed during the 1930s by Carl Zeiss AG in Jena . Following WWII division of Germany and the founding of Carl Zeiss (West Germany) in Oberkochen (while the original Jena plant was located in East Germany), each factory developed its own line of projectors. . </P>

In which city was the world's first planetarium projector installed in 1923