# NavList:

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

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Re: Tables of Trig Functions and Logs of Trig Functions
From: Gary LaPook
Date: 2007 May 02, 16:42 -0700

```Gary LaPook wrote:

I like to use my K&E  slide rule sometimes for sight reduction just to
stay in practice. Obviously it lacks the precision of a digital
calculator but you do get useful answers.

George Huxtable wrote:

>Robert Eno wrote-
>
>| Essentially, for the same reason why I persist in using a sextant: the
>| challenge of doing it the hard way. Oddly enough, I find it rather
>| therapeutic to perform the odd sight reduction the old way using the trig
>| and log tables. It also hones my basic understanding of the mathematics
>| behind the calculations. It also gives me another level of independence of
>| electronic gadgetry should the latter fail me absolutely some day. Don't
>| misunderstand me: I still use a scientific calculator (and if I am
>| particularly impatient, my Celesticomp V) but for every round of sights
>that
>| I take, I reduce at least one or two using the tables: the hard way.
>
>Comment from George-
>
>I agree with that, in every respect but one, where Robert writes "It also
>hones my basic understanding of the mathematics behind the calculations."
>And for this reason: because the basic simple spherical trig expressions
>have been bent, twisted, and manipulated, quite beyond recognition, in order
>to avoid additions and subtractions, once the navigator has "gone into
>logs". This results in him going blindly through the set procedures "by
>rote", without much chance of understanding the steps involved, and simply
>accepting the result that comes out of that process.
>
>And so (in my view) doing all that trig manipulation by a pocket calculator
>provides a breath of fresh air. Now that logs are no longer called for, the
>basic trig expressions can be worked through, bit by bit, just as they come
>out of the textbook. It's easy to see what contributions the individual
>terms in the expressions are making. It's easy to try out simplifications
>and short-cuts, such as taking the sine of an angle near 90 to be exactly 1;
>that sort of thing, when you can see what you're actually doing.
>
>As I see it, having to use logs and lookup tables (and in their time, there
>was really no alternative) set back the understanding of what navigators
>were actually doing. Now we can enjoy the privilege of doing the
>mathematical manipulations absolutely straight, and far more accurately than
>we will ever need. How our navigational forbears, as recently as thirty-odd
>years ago, would have relished that opportunity!
>
>George.
>
>contact George Huxtable at george@huxtable.u-net.com
>or at +44 1865 820222 (from UK, 01865 820222)
>or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
>
>
>>
>
>
>
>

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