Refers to the facility, the projection device, or the show itself. Common in science museums and educational contexts.
週末に子供とプラネタリウムに行った。
I went to the planetarium with my child on the weekend.
The new planetarium projector is very high-performance.
I went to the planetarium with my kids over the weekend.
I watched the winter constellations at the planetarium.
That science museum runs planetarium shows three times a day.