A New Graphic Method in Nautical Astronomy

Abstract

A NEW departure of some little interest has been recently taken in America in the publication by the United States Hydrographic Department of a new chart, or diagram, for finding readily by a simple graphic process hour angle or azimuth at sea. So far as azimuth is concerned, a diagram of this nature, known as Weir's Azimuth Diagram, has been in use for many years, but in that case the hour angle is made use of as a datum, whereas in the new diagram the altitude takes the place of hour angle as argument; and, as an altitude can be observed at sea with much less trouble than hour angle can be deduced from chronometer time, some labour is saved by its substitution.