This diagram has been prepared to simplify the method for the identification of stars described in No. 123 of the U. S. NAVAL INSTITUTE and shows the relation
Sin t cos d= sin Z cos h;
from which the declination is found after finding the hour angle from the Azimuth Tables—the azimuth having been observed or found from the Azimuth Diagram.
2. To Find the Star's Declination from the Diagram.
Enter with the azimuth on the margin; the intersection of the horizontal line through this point with the curve corresponding to the true altitude fixes a vertical line, the intersection of which with the horizontal line corresponding to the hour angle previously found, determines the curve corresponding to the declination of the body.
3. Thus in Problem 1, we have Azimuth= N.74°W.; Hour Angle= 72° 24' and Altitude= 29° 30' and we find the Declination= 28° 30'.
Problem 2. Azimuth= S. 110° 25' W.; Altitude= 19° 51' 20"; Hour Angle= 64° 30’; hence we find the Declination= 12°30'.
Problem 3. Azimuth= S. 64° 37' E.; Altitude= 25°55'; Hour Angle= 58° 04'; Declination= 16° 15'.