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An illustration of the position of the viewer in the dome apparatus, shown in side-view cross-section. The eyes are in line with the central disc, labelled C. The dotted line labelled A shows the position of an opaque screen that obscured the view of the discs prior to the artists being properly positioned in the apparatus. The upper and lower limits of the visual field are indicated. The eyes of the viewer are located 450 mm from the central disc C.
