# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Azimuth and Declination formulae**

**From:**Peter Fogg

**Date:**2005 Jul 15, 10:29 +1000

Peter Fogg wrote: (I did!) > Have found this one: (Azimuth formula) > > Chuck Pettis' Azimuth equation: > AZ = acos ((sin D - (sin L * sin H) / (COs L * COs H)) > where H = horizon height (degrees) > > (The H has me puzzled. Perhaps it refers to Dip, or could it refer to > altitude?) > > Here's another: > > Z = cos^-1 * [sin Dec - sin Lat * sin h / cos Lat * cos h] > where h = vertical angle to the sun corrected for parallax and refraction > (h = altitude?) I think they are the same sine method. The first version may be for terrestrial navigators, with its added factor of 'horizon height'. Along the way, I found a formula for the calculation of the Sun's declination: Dec = 23.45 sin (360/365.25) Its such a simple formula even I can understand it. Its the maximum declination of the sun expressed as a proportion of its change. Here's another version: Dec/23.45 = sin(0.985*t) 0.985 is a truncated version of (360/365.25) and t = the number of days from the vernal equinox or t = (inv sin(Dec/23.45))/(360/365.25) These formulae come from: www.geomancy/org./sunfinder