# NavList:

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

**Time sight of the sun, a navigator's morsel.**

**From:**Zorbec Legras

**Date:**2004 Sep 28, 23:02 +0000

Time sight of the sun, a navigator's morsel. The formulae Method 1 : cos t = (sin h - sin L sin d) / (cos L cos d) (1) Method 2 : hav t = cos S sin(S - h)/ sin p cos L (2) with : S = (h + p + L)/2. Formula 1 can be solved by a semi-logarithmic computation Formula 2 can be solved by a logarithmic computation and in fact formula (2) is derivated from formula (1) which is derivated from de fundamental formula : sin h = sin L cos p + cos L sin p cos t with : p = 90deg - d Extracting t we have : cos t = sin h - cos p sin L/ sin p cos L (1 bis) Using the versine we have: 1 - cos t = (sin p cos L + cos p sin L - sin h) / sin p cos L which gives: 1 - cos t = (sin(p + L) - sin h)/sin p cos L and 2 hav t = 2 sin((p+L-h)/2) cos((h+p+L)/2)/sin p cos L With: p + L + h = 2S and : p + L - h = 2(S-h) we get finaly the formula (2) to avoid a substraction of log, formula (2) is rewrited so : hav t = cos S sin(S - h) csc p sec L (2 bis) csc = 1/sin, sec = 1/cos. which become in casu : log hav t = log cos S + log sin (S-h) + log csc p + log sec L (2 ter) ------------------------------------------------------- just for fun ------------ -- ___________________________________________________________ Sign-up for Ads Free at Mail.com http://promo.mail.com/adsfreejump.htm