GB218527A - Astronomical appliances for educational and other purposes - Google Patents

Abstract

218,527. McEwan, D. Sept. 15, 1923. Globes. - Combined astronomical and geographical charts for use in teaching astronomy, navigation, or geography, or for navigational or other purposes, comprise hollow hemipheres bearing representations of the stars and of geographical features, an indication being given of the points of the earth at which stars are overhead at a chosen time and, when the charts are used in an adjustable stand, of the position of the stars relatively to the horizon at any time or place. Each chart may comprise a single translucent hemisphere marked with the North or South terrestial hemispheres and with twenty-four meridians representing the hour graduations and provided with holes indicating the stars in a celestial hemisphere so that, when the chart is viewed from the interior and illuminated from the exterior, the stars and geographical features occupy the relative positions in which they would be at midnight of a given date and longitude. Alternatively, each chart may comprise an inner translucent terrestial hemisphere 24, Fig. 5, and an outer concentric hemisphere 23 perforated at 19 to represent the stars, the hemispheres being relatively adjustable to give the positions of the stars at any time. Either form of chart may be mounted in a frame 10, Fig. 1, pivoted about the axis A, B at one end of an arc 3 and adjustable by means of a knob 9 graduated in hours, the arc 3 being adjustable in a guide 2 on a stand 1 by rack and pinion gearing from a knob 7. A curved bar 15 mounted at the ends of a horizontal bar 16 supported from the guide 2 represents the horizon, the position of the stars relatively to which at any place and time is demonstrated by adjusting knob 7 until the angle X is equal to the latitude of the place and by rotating the knob 9 and so the celestial hemisphere for time adjustment. Specification 28546/12 is referred to.