# NavList:

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

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Hughes, Dreisonstok and dec~lat
From: David C
Date: 2020 Apr 13, 14:58 -0700

The lockdown is giving me time to study various tables in detail. For example, I have learned that Aquino (HO 200) allows use of the DR position rather than requiring an asumed position. The same applies to Ageton (HO 211).

I took several sun sights and decided to reduce them using Hughes' tables. The first step was to learn Hughes'  method. After I had successfully worked one sight I performed sanity checks with AP3270 (HO249), HD486 (HO214), NP401 (HO229) and the cos formula.  Then I decided to try HO 208 Dreisonstok. I found that these tables are similar to Hughes' but with one big difference -  the meaning of dec ~ lat.

Back on 21st  June 2016 Franks wrote   (dec ~ lat) = abs(dec - lat).

The worked examples given in the tables show that

Hughes   K~d = abs(K-d)

Dreisonstok   d~b = abs(d+b)

I have  worked the same sight with both Hughes' and Dreisonstok and can confirm these conventions.

With reference to d~b, page  69  of Dreisonstok states    ".......add if the signs are alike, subtract if unlike."

DavidC

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