Next message: John Kabel: "Abbreviation of Nautical Mile"
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
