By mounting the lamps at different distances from the transparency and different positions inside the box, theywill project to different places on the dome and the galaxies will have different sizes and shapes. If you have a drive that will move a single lamp, the projected image will move across the dome. The lazy susan bearing is driven by a 3-rpm motor mounted on the top of the box with its shaft parallel to the plane of the lazy susan bearing. A small wheel is attached to the shaft of the motor and rests on the edge of the bearing. See Drawing 2 .
Opaque projectors can produce very realistic tumbling asteroids or rotating planets on the dome.
These projectors require a very bright light wource shining on the object to be projected. Good ventilation and fan cooling are a must for this sort of projector. The light reflected off the object is focused onto the dome by a projection lens. The object may be a plaster model of an asteroid, pitted and painted appropriately and mounted on a motor shaft. A small ball painted with oceans and continents can represent a suprisingly realistic planet as seen from space.