Patent GB-244448-A (GB)
Title: Improvements in devices for illustrating the apparent movements of the stars and planets
IPC: G09B27/02
Filed: 1925-11-26
Abstract: 244,448. Zeiss, C. [Firm of]. Dec. 11, 1924, [Convention date]. Planetaria.-Apparatus for projecting images of the stars on a hemispherical screen comprises two groups of projection-devices carried on a support, each group consisting of a number of projectionappliances adapted to receive light from a source common to the respective group, the groups being arranged to project images of the whole fixed-star sky in such a way that the projection appears to be effected from a point midway between the groups. The apparatus is mounted on two bars a', a<2>, Figs. 1 and 2, suspended horizontally by ropes o<1>, o<2>, and held in position by other ropes o<3>, o'. Pivotally mounted in the bars is a body n in which a carrier b is carried to rotate about an axis X-X. A shaft d is mounted in the carrier b so that its axis Y-Y is at an angle of 23¢‹ to the axis X-X. The body n is rotated in the bars a', a<2> until the axis X-X is at an inclination to the plane of the horizon equal to the latitude of the place at which the apparatus is used, an index n<3> and scale a<3> being provided for this purpose. A set-screw a<0> serves to secure the apparatus in adjusted position. The carrier b is rotated by gear-wheels b<1>, c' from a motor c<2> mounted on the body n. The shaft d is rotatable about the shaft Y-Y and is fixed in position by the set-screw (d<0>. Screwed to the ends of the shaft d are collars d<10>, d<11> carrying plates d<2a>, d<2b> between which known devices for projecting the images of the sun, moon, Mercury, Venus, Mars, Jupiter and Saturn are mounted. To the outer of the plates d<2a> and d<2b> are fixed hemispherical casings carrying a number of projection-appliances d'a, d<7b>. Glow lamps d<8a>, d<8b> common to the respective projection-appliances and of which the filaments are on the axis Y-Y and enclose the centres of the casings, are provided, and the appliances are mounted so that images of the whole northern and southern fixed-star sky can be projected nn the screen. The images on the lantern plates are so marked that projection appears to come from the point of intersection E of the axes XX, Y-Y. Projection-appliances p<1> - - p<6> are mounted on the apparatus to project circles corresponding to the ecliptic, and other appliances q<1> - - q<4> are provided on the bar a' to project a circle corresponding to the meridian. As the appliances q<1>, q<2> are in such a position that they are obscured by parts of the apparatus during rotation, further appliances q<1a> and q<2a> are provided on the bar a<2> and are arranged so that the lines projected by the two sets of appliances coincide. The apparatus is so mounted that the point E is also the centre of gravity. In a modification the bars a<1>, a<2> are supported on frames equidistant from the point E. The Specification as open to inspection under Sect. 91 3) (a) refers also to a modified arrangement, shown in Fig. 4 (Cancelled), for use when the supporting-means is so thick as to impede the projection. A bar j<6>, slideable in a guide e and rotatable in a holder j about an axis N-N parallel to the axis Y-Y, is provided with two projection-appliances j<1a>, j<2a> so arranged that the images projected on the screen overlap. This subject-matter does not appear in the Specification as accepted.