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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2019 Jul 12, 10:01 -0700
I have to admit that I forgot everything about haversines five minutes after an astro examination 1973, so I thought it was time I gave them another bash. (The instructor was Capt Garcia USAF, and he started the course by saying the exam would be in Spanish; fortunately, it wasn't) As far as I can see the sunrise situation makes Hc effectively zero degrees, and Hav0=0, so the Z equation (courtesy of Wikipedia)
Hav(Z)=Hav(90+- Dec)-Hav(Lat-Hc)/1-Hav(Lat-Hc)-Hav(Lat+Hc)/1-Hav(Lat-Hc)-Hav(Lat+Hc)
reduces to HavZ(90-Dec)-Hav(Lat)/1-2Hav(Lat)
so HavZ=Hav79.18-Hav13.13/1-2Hav13.13
=.4072-.0132/1-2(.0132)
=.3940/.9736=.4047
so Z=Zn in this case, because LHA>180 = 079degrees true.
Why was the skipper smiling? Perhaps the lightening bolt finally shocked him into realising what must have happened to the remainder of the ice cream. DaveP
