GB156033A - Improvements in apparatus for use in solving problems in nautical astronomy or navigation - Google Patents

Abstract

156,033. Eldridge, R. A. April 12, 1920. Spherical - trigonometry calculators for use in solving problems in nautical astronomy and navigation comprises a base 1, Fig. 1, on which is mounted a rotatable disc 3, a sliding member 9 adapted to move parallel to itself, and a graduated drum 13 or plane surface 20 with which the sliding member 4 co-operates. The disc 3 is divided into degrees around its circumference, and is provided with a circle 5 having marked thereon orthographical-projection lines 6, 7 representing respectively hour angles and declinations of known celestial bodies. The member 9 which is adapted to slide in slots 10 in the base 1 carries an azimuth scale divided by orthographical projection into degrees and hour angles and cooperates with altitude scales 8 marked on the base 1. The member 9 is provided with a pair of racks 11 which engage pinions 14 on the drum 13 so that it may be turned in synchronism with the movement of the member 9 or it may be turned by hand independently of the member 9. The ends of the drum have scales 16 corresponding to the scales 8 and the circumference of the drum is divided orthographically by lines 15 representing degrees and hour angles. A scale 18 corresponding to the azimuth scale co-operates with the drum 13, and a latitude pointer 19 is provided on the base 1. In a modification as shown in Fig. 4, the member 9 is connected by links 21 to a scale 18a which is adapted to move over the surface 20 graduated in the same manner as the drum. The Specification describes the calculation of the unknown parts from three known parts of the spherical triangle such as the hour angle and azimuth from the known data latitude, and true altitude and declination of the celestial body. The Specification also describes the method of finding the great circle course and distance between two points of known latitude and longitude. Specification 14008/08, [Class 97 (ii), Surveying &c. instruments], is referred to.