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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Hav-Doniol
From: Stan K
Date: 2015 Jun 13, 08:45 -0400
From: Stan K
Date: 2015 Jun 13, 08:45 -0400
Last night I sent a message to Greg Rudzinski describing a really silly, even obvious, mistake I was making in using the Greg/Hanno hav-Doniol sight reduction method. This got me thinking (something I apparently should do more often), so I went through the fer3 archive looking at all the posts regarding longhand sight reduction. This is what came out of it:
Greg presents two sets of formulas:
n = hv(L - d) m = hv(L + d) same name
n = hv(L + d) m = hv(L - d) contrary name
where L (latitude) and d (declination) are unsigned (absolute) values, i.e. 40ºN and 40ºS would both be represented as 40º.
Hanno appears to prefer a single set of formula, equivalent to the "same name" formulas above (though he uses one different letter), where L and d are signed, i.e. 40ºS would be represented as -40º.
These are different approaches but are functionally equivalent. What I would like to know is if anyone has a strong feeling as to whether either of these approaches would be better than the other one in a classroom environment, that is, whether students would have an easier time understanding, and instructors would have an easier time teaching, one compared to the other.
Stan
