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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sun Azimuth
From: Bill B
Date: 2013 Jan 09, 17:55 -0500
From: Bill B
Date: 2013 Jan 09, 17:55 -0500
A quick way to get a pretty accurate azimuth for rise or set if you know your latitude: Estimate sunset or sunrise time for your lat and estimated long using the almanac. Calculate the declination for the approximate time of rise or set. Locate the refraction correction for 0d upper limb in the almanac. It will be -49!7 plus/minus 0!1. Use this as your HC. Use your lat, HC and declination in the standard equations for calculating azimuth. No extra tables or equations needed. This should also work for stars or planets using -33!8 as your HC. =================================== Time of sunset or rise given exact lat and long. Swap out the HC and declination above. Use the standard azimuth equation and it becomes a classic time sight yielding LHA. LHA combined with your long determines your target GHA. Subtract the hourly almanac GHA just smaller than the GHA you calculated above and convert arc to time. (The same as determining LAN given longitude.) The UT of the hourly almanac you used plus the arc to time from above is your UT rise or set within the limits of low-angle refraction gremlins and bodies being extinguished by the atmosphere. Bill B.
