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The so-called concentric seat arrangement is the most suitable for astronomical presentations. The edge of the dome is the (mathematical) horizon at the same time - the plane of reference for the rising and setting of the celestial bodies. Fulldome videos may also specially be produced for concentric seating.
Slide and video projections are projected in a single direction. There will always be seats where visitors are forced to crane their necks to see properly. To avoid that, either the pictures are projected onto two or even three different positions in the dome, or all the seats are aligned for the same viewing direction.
The unidirectional seating is the more common type at present. The audience sits in rows curved in varying degrees. The planetarium projector has been provided with a vertical axis to permit the southern sky to be moved to the north and the northern sky to the south, if necessary.
However, the audience still has to gaze upward. Tilting the auditorium and, as a result, the projection dome bring some comfort. The audience sits in much the same way as in an amphitheater. In astronomical terms, tilting makes little sense.
In some cases the dome aperture is less than 180 degrees. The planetarium projector thus can be placed below the springline of the dome. Projections from the edge of the dome (fulldome video etc.) can be directed across the dome's center without causing shadows by the central planetarium projector. | |
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