Small projector for representing the starry sky

摘要

The projector can be used for didactic purposes, e.g. school, public observatory. The projector shows the starry sky for arbitrary geographical locations and arbitrary times. The diurnal movement of the starry sky can be represented in time lapse. The device consists essentially of three concentrically arranged spheres. From the inside outwards: projection sphere (K1), star sphere (K2, analyser), polarisation sphere (K3). The star sphere is freely rotatable inside the projection sphere. Stars are realised on the star sphere surface by circular holes of different size (magnitude) and colour and imaged by point light lamps (PL) in the centre on the projection sphere, which is sprayed white. Degree grids and figurative representations of the constellations can be faded in and out depending on the mutual position of the star and polarisation spheres. The planets and moon are represented by small individual projectors which are mounted on a plexiglass strip (ecliptic) spanning the star sphere. The positions of the star and polarisation spheres can be varied by geared motors. Rotation pulse transmitters (RIG) transfer changes in position to a logic circuit. This enables all the functions of the small projector to be controlled by computer.