NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: What's "under the hood" of the Raft Book?
From: Greg Rudzinski
Date: 2017 Oct 21, 10:47 -0700
From: Greg Rudzinski
Date: 2017 Oct 21, 10:47 -0700
Tony,
-16' is just the semi diameter of the Sun to be applied to the 0° Sun upper limb Hs value. Inside front cover of the Nautical Almanac has 0° refraction -33.8'. Now also subtract dip for someone sitting in a raft -2.0' then -16.0' semi diameter of Sun for a grand total -51.8'. This is a negative Ho altitude which may cause sight reduction trouble for some. A work around is to hand make a kamal from 1° to 4° so that a positive Ho can also be observed and eliminate all the negatives. I like using 1 cm per 1° scale held at 22 inches from eye. Attached shows a variation of this concept using a standard index card with scale to 9° using a quarter inch hole filtered with solar film.
Greg Rudzinski
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