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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Theo Honohan
Date: 2026 Jul 6, 23:12 -0700
The Zeiss planetarium was originally conceived as a "Ptolemaic" display just like this.
Since planet and sun locations were projected onto a dome, the mechanical approach was to use a little Copernican models for each planet: each consisted of a moving pivot point for Earth and one for the particular planet. The line between the two planets/points designated the direction in which the attached projector sent the image of the planet.
By using eccentric pin-and-slot mechanisms, Keplerian orbits could be accurately recreated. Orbital inclination was incorporated as well.
So the Zeiss projectors had a stack of nine little two-planet orreries to handle simulating the appearance of the solar system from Earth
The Internet Archive has a digitised copy of the book Geared to the Stars, which gives a fairly good description of the mechanism. https://archive.org/details/gearedtostarsevo00king






