NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude and Longitude by "Noon Sun"
From: Bill Noyce
Date: 2005 Jun 7, 10:35 -0400
From: Bill Noyce
Date: 2005 Jun 7, 10:35 -0400
There are courses taught to the spouses of private pilots, that teach the bare minimum needed to get the plane down safely if something happens to the pilot. I see Frank's method of navigation by noon sights as the same kind of thing. The main argument in its favor is that it is easy to remember. If you were taught this method a few years ago and never used it, you could probably reconstruct it when called upon. If you have any kind of mental picture of how the sun moves through the day and through the year, you can work out the logic of the sights. It can be done "by hand", with pencil and paper, without using any tables. And the only almanac data you need is the sun's GP, tabulated perhaps once per day, and a rough value for dip and refraction (both small on a small boat in summer). No need to remember the magic number 15.3, or a way to compute trig functions. You do need to remember that 1 minute of arc = 1 nautical mile, but that's about it. I would hope that students of this method also get told that there are more general methods, and a sketch of how they work, so they realize there's more that they haven't learned yet. Really, the only added complication is computing Hc from an assumed position, so the noon sight, which might be easier to visualize, seems to me to make a good introduction. Unfortunately, computing Hc requires more support -- either bulky tables, or a calculating device, or a longish pencil-and-paper procedure using short tables. These are less likely to be available if the need for celestial navigation appears unexpectedly. -- Bill