A Device of "the Diagram for Distinguishing the Mark of the Azimuth"

Abstract

In order to distinguish the mark of the calcurated azimuth N or S, navigators have used "the tabb of the altitude on the prime vertical" complaining that this method is too troublesome through the process. Considering this point, we have newly devised a simple method in which they should use a diagram on the plane of the observer's celestial meridian instead of the above table for the same purpose, and then in this paper we shall introduce the new method in anticipation to the practical navigation. I Summary explanatron of the new method with an example (Refer to Fig.2 & Fig.3) Problem: Celestial body=Fixed star "Altoir", Hour angle=301°7', Latitude=25°58' N are given. Find the mark of the azimuth N or S. Solution: Plot Altair's position on its dotted line (repr: diurnal circle) according to given hour angle. Take the zenith on the outer circle (repr.: observer's celestial meridian) according to given latitude and draw a straight line (repr.: prime vertical) from the zenith to the original centre (repr.: E or W point). Then Altair's position is southerly from this line, therefore the mark of the azimuth is "S" II Excellent points of the new method in comparison with the former. (i) In spite of the marks and quantities of declination and latitude, we can directly distinguish the mark of the azimuth to the effect of saving time. (ii) At the first glance we can easily get the relation between the celestial body and the observer ; through the process, therefore, we have no fear of insecurity and can avoid unexpected mistakes. (iii) This diagram rather have the higher accuracy than "the table of the altitude on the prime vertical".