A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2014 Jun 9, 09:08 -0700
The attached index card shows a sight reduction done longhand to 4 places using cosine and haversine tables. This is a manageable method for those who want to avoid logs. The beauty of the haversine table as presented in Bowditch is that LHA can be directly entered and formula rules are simple.
hav z = hav(L~d) + cosL cosd havLHA
Hc = 90 - z
L-d same name
L+d contrary name
A compact set of cosine haversine tables, Ix diagram, and LTA would make a nice sextant box booklet. The question now is can a 10" sliderule sight reduction do a better job if scaled with haversines ?