# NavList:

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

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Re: Compass error correction
From: John Huth
Date: 2010 Jul 5, 04:16 -0400
Byron -

Yes, the technique looks very straightforward and intuitive.    I like doing chart-work, although I'm capable of shifting this sort of technique into trigonimetric-ese.   When I've taught classes graphical techniques, it usually sinks in, but invoke a trig table (or sine button), the students turn pale.    I think it may be one level of abstraction too much.   When looking at navigation problems, the mind tends to first think about things in terms of maps - graphically.   If you hit the next level of abstraction, that's where difficulties emerge.

I've been struggling with the very issue of teaching celestial to an audience that is not predisposed to a lot of mathematical sophistication.     Although St. Hilaire is a very powerful technique, it's not something that's easy to call up from memory.    I have a rather arduous way of memorizing the two main spherical trig formulas that start from very simple cases (e.g. one is rising and setting azimuths, given a declination and latitude) and add complexities to the limiting cases.   But even this is too much.

I think Frank and others have talked extensively about methods used before St. Hilaire and they make a lot of sense - e.g. the ones used on whaling vessels.    Unfortunately they seemed to have been in a state of flux.  But there are easy ways of thinking about the equation of time, when are good times to get an accurate longitude, when are good times to get an accurate latitude, easy ways to do corrections for dip and refraction.

The book "Emergency Navigation" by David Burch is a good start.    In teaching it, I think it might be good to supplement some of what he (Burch) says with better explanations, like why the refraction correction works the way it does, why dip works the way it does, so that the sign of the effect becomes intuitive, as well as the magnitude.

Just some thoughts.

John H.

On Sun, Jul 4, 2010 at 3:35 PM, Byron Franklin wrote:

Can't make it any easier than that,Navigation must be simple or it will not be used. I am working on making Celo easy to learn, I think I have a a different veiw than how it is being taught. Why do seaman not use Celo today? It is to difficult. It must be made easy.

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