I have to admit a weakness for planetarium projectors. I started looking at planetaria more seriously around the same time as I was researching dioramas. The combination of material and pictorial space was resonant with the dioramas with the added pleasure of the temporal dimension. Added to that is the projector, an analogue computer able to register the night sky in either hemisphere to represent any moment over a several thousand year span. As instruments they embody a knowledge and understanding of astronomy. Some of the mechanisms are under precise control while others, such as the eyelids on the spherical projectors at either end just fall with gravity with weights to stop the sky below the horizon being projected onto the audience, are dependent on the situation of the projector. I am working on a simple analogue computer at the moment for the new drawing instruments and the planetarium projectors, along with the Norden bombsight, have been helpful for finding my way.
The projector above is from the Griffith Observatory in Los Angeles, which has been replaced by a digital version. The images below are from the book Captured Stars.
You might be interested in the Mel Bochner and Robert Smithson article structured around the (old) Planetarium at the American Museum of Natural History in New York in Art Voices Fall 1966, discussed in an article in the September 2006 Artforum by Mel Bachner.