GB1442152A - Planispheres - Google Patents

Abstract

1442152 Planispheres W A EISENHAUER W P ELLWOOD and L E EISENHAUER 3 July 1973 [3 July 1972] 31716/73 Heading G4B A planisphere, enabling navigational as well as astronomical calculations, comprises a disc 24, Fig. 3, bearing a map of the position the stars of the northern hemisphere would have, looking down at them, if the stars were projected from their celestial positions towards the centre of the earth, a reference line (63, not shown) indicating the radial position of the first point of Aries on the map, a disc 22, Fig. 8, overlying disc 24 and bearing a map of the world, a reference line 50 indicating the radial position of Greenwich on the map of the world, and a disc 26 overlying disc 22 and bearing horizon indications 34 for respective latitudes. Disc 24 also bears a date scale 56, degree scales 58, 62, and an hours of sidereal time scale 60. A disc 14, Fig. 3, bears navigation east and west scales 92, 94 and underlies disc 24. A reference rule 28 (not shown) overlies disc 26. The rule, disc 26 and disc 22 are transparent. On the other side of disc 14, which is the largest diameter disc, are further discs, Fig. 2 (not shown), including a Greenwich mean time and sun angle disc, discs for standard and local time, and discs similar to discs 22, 24, 26, except that this disc 24 bears a map of the positions of the stars of the northern hemisphere as viewed from earth, Fig. 4 (not shown). The other (hidden) sides of discs 24 may bear corresponding ground position and overhead star maps pertaining to the southern hemisphere, Figs. 5 and 6 (not shown), so that the device may be adapted for use in that hemisphere by removing the central pivot (not shown), common to all discs/rules, inverting both discs 24 and re-assembling the device. Corresponding discs or rules on opposite sides of the largest disc 14 may be connected together in pairs.