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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Smart and Shearme Position Line Tables
From: David C
Date: 2020 May 5, 21:25 -0700

DavidP wrote

Will you send the 1958 Bowditch formula for co-alt, co-dec, and hour angle, because it should provide a clue to a co-alt, co-lat, hour angle formula you were looking for?

I have typed the following because from experience pasting into the navlist editor does funny things to the format. I hope that I have typed it correctly.

d h t   sinz = sin t cos d sec h  Bowditch  1958 p 567

d h l    cos z = (sin(d) - sin (l)xsin(Hc))/(cos(l)xcos(Hc)))  Bowditch 1995 p 341

also   hav z = (sin(s-L)sin(s-h)sec h  sec l   Bowditch 1958  p567

where s= 1/2(h+l+p) and p = (90 ~ dec)

also  hav z = hav (l+-d) +hav h cos l cos d  Norie 1970 p XIIV

d t l   cot z =tan d cos l/sin t  - sin l sin t   Bowditch 1958 p569  and 1995 p341

also cot z sec lat = tan d cosec t -  cot t tan lat   Norie's ABC tables

C                 =         B          +-       A

yet another version  tan(z) =(sint /cos l)/(tan d - tan l * cos t)   http://fer3.com/arc/m2.aspx/Altitudeless-Azimuth-formula-TonyOz-nov-2019-g46143

even more    tan(z)  = sint /(cos l tan d - sin l cos t)  http://fer3.com/arc/m2.aspx/Altitudeless-Azimuth-formula-Howard-nov-2019-g46147

The index for Bowditch 1943 is, strangely, at the front of the book so I nearly missed it. This volume gives the haversine d l h formula and the sin  t d h formula.

Note that none of the formulas come from the AMN, which is the original point I was making.

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