Not too long ago and not too far away, @oldben pointed us at an episode of James Burke’s Connections:
I just finished watching it (as usual, a sweep through history, from the astrolabe to mass production) and the credits led me to this video explaining the origin and history of the building, and the PDP-8 within:
Just before the 10min mark we hear DEC offering a rack mountable 4k PDP-8 with teletype for $10k dollars “minus educational discount”.
I also found a single-page article Van Der Beak’s “Cine Dreams” in Rochester (PDF) about the planetarium:
The planetarium contains an automated control system which in large part makes an eight hour show possible. This system uses a PDP-8 computer to record information from a special effects control panel. This enables the operator to see how an effect will look on the dome before recording it in the computer. The programs are usually recorded in thirty to forty-five-minute segments. When the program is played back, the computer runs the special-effects control panel. If the computer should break down, the show can be run manually as it was when the snow was originally recorded.
Edit: another still from the video
and another