GB107784A - Improvements in or relating to Star-guides for Night Marching. - Google Patents

Abstract

107,784. Goldsmith, E. T. June 6, 1916 Solar and stellar compasses.-A star-guide for use in selecting a star for night marching comprises a star map, a protractor for determining the magnetic azimuth or compass bearing of stars on the map, and means for indicating the correct relative position of the protractor and map for the date and time at which the guide is being used. As shown, the star map B is slidable in guides formed by inturned flaps A<2>, A<3> on the edges of a stiff cover A, the map being provided with a calendar which is read against the end of the flap A'. The map is projected so that areas bounded by two given parallels of declination and by equally spaced lines of right ascension are equal in size and shape, and, as shown, represents a wide equatorial belt with a repeat portion, the areas referred to being rectangular. The protractor C, which is transparent, is also slidable in the guides formed by the flaps A<2>, A<3>, and has an arrow C' which is read against a time scale on the flap A<3>. The protractor is set out with lines of magnetic bearings and lines of altitude in accordance with the latitude at which the guide is to be used, and has a line marked on it which, when the guide is being used, is maintained in register with a line on the map indicating the celestial equator or a line parallel therewith. An arrow C<2> may be provided on the protractor for use instead of the arrow C' when the observer is using "summer time." The bearing of the sun at any time may be obtained by setting the protractor to that time and reading the bearing of the appropriate date in the figure shown printed on the left-hand end of the case, or in a similar figure on the opposite end of the case. The case may be capable of being folded at A' to halve its length when not in use, and a flap A', and an elastic band to hold the parts in the folded position may be provided. The map may be printed on the case and allowance for the date may be made in determining the time at which the protractor should be set. According to the Provisional Specification, the protractor may consist of oiled silk carried on a V-shaped wire frame of which the yoke is bent out to form a fingerpiece and is given one or more turns to render it springy.