NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: h.a.c. van Asten
Date: 2012 May 20, 00:37 -0700
Simply use sin d(i) = sin d(m) . sin L , where d(i) is the declination of the day , d(m) is the maximum (sun´s) declination 23 deg 27´ , and L is the longitude of the sun as measured from the closest solstice . Example : compute for the declination @ May 20 , 2012 . Solution :
May 20 is abt 60 days short of June 21 , or 60/90 x 90 deg = 60 deg . sin d(i) = sin 23-27´ x sin 60 = 0.39795 x 0.86603 = 0.34464 => d(i) = 20.16 (20 deg 09´.5).
And check by the 2012 NA : the result matches May 20 , 1700 hrs UT , dec 20-09´.8
For most navigational computations , p.e. by formulae , the accuracy is for 1 day good enough to avoid ambiguity or error .
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