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Celestial Navigation When Your GPS Fails

by Mark Breach

142 pages; quality trade paperback (softcover); catalogue #04-0495; ISBN 1-4120-2667-9; US$26.29, C$33.29, EUR21.63, £14.99

The ultimate manual for bluewater navigation, complete with all the forms and data, for when your electronics fail.

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about the book      about the author      excerpts and table of contents      catalogue info

About the Book Celestial Navigation When Your GPS Fails is about finding position at sea from the Sun, Moon, planets or stars. If you have a sextant and the time, in both senses, this book contains all you need to find your position. This book is for real and aspiring bluewater sailors; those who leave the sight of land and rely on various electronic devices for navigation. When satellite navigation fails because of seawater in the electronics or just plain battery failure then being lost at sea is a life-threatening situation, especially when night falls. Everything you need is here, apart from the sextant and a watch. A calculator is handy but not essential. There is complete instruction on how to use a sextant, on making astronomical observations and on how to do the calculations with or without the forms. All tables and the forms needed to make the calculations are available. You do not need any further almanacs or tables for the next ten years! The text explains the celestial framework in which we must operate, with particular reference to the way that the Sun, Moon stars and planets appear and the principles of astronomical navigation. The sextant is described along with its errors and the necessary corrections that need to be applied. Reductions of observations for dip, refraction, semi-diameter of bodies and parallax are covered. With the theory well established, the practicalities of position finding are explained in detail. There is a chapter on the origins of some of the formulae used for those who want a deeper understanding of the mathematics involved but this may be omitted by those who prefer to focus more on the practice of position finding. The main text concludes with a detailed worked example and blank forms for your own observations of celestial bodies and for the calculation of position. All the tables that you will need are included. All the other tables that you might need, depending on when and where you are going, are on the Celestial Navigation website.

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About the Author Dr Mark Breach, MA MSc PhD FRICS FInstCES FRAS AFRIN, is a Principal Lecturer at Nottingham Trent University, England. He lectures in Mathematics, Geodesy and Navigation. He holds Master's degrees from Cambridge and Oxford; his PhD was concerned with astronomical positioning. He is an Associate Fellow of the Royal Institution of Navigation and a Fellow of the Royal Astronomical Society, the Royal Institution of Chartered Surveyors and the Institution of Civil Engineering Surveyors. Born and brought up in Falmouth, England, he has been around boats since a boy. From an Atlantic crossing under sail in his teens (long before the luxury of GPS) he has crewed, skippered and navigated thousands of nautical miles with his yacht, SunArise, kept on the River Humber; the East Coast of England and Scotland is his current cruising grounds.

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Excerpts and Table of Contents

Table of Contents:

Preface

Celestial Navigation is about finding your position at sea using the Sun, Moon, planets or stars. Provided you have a sextant and the time, in both senses, this book and associated website will give you all you need to find your position. Even if you do not have precise time, you can still use observations with your sextant to find your latitude.

This book describes the use of the sextant and how to find position from your observations with full worked examples. Here are all the forms and tables you will definitely need. The website also has all the same forms and tables, and all the tables that you might need, depending on where and when you put to sea. Therefore, you only need print the pages that directly relate to your intended voyage.

"Why bother with astronomy?" you might say, when you have a fixed GPS and perhaps a handheld GPS on board. Reliance on a single system at sea for any purpose, including navigation, is unwise. Imagine this scenario: you are in mid-Atlantic and a large lump of the "briny blue" comes down the companionway flooding the boat's batteries and engine. By the time you have bailed out, you discover that the handheld GPS has sunk to the bottom of the bilge along with the calculator and laptop. The radios have suffered a similar fate. So, distinctly shaken and very much stirred, you regain control of the boat and, as there is no immediate danger, there is no need to activate the Emergency Position Indicating Radio Beacon.

What next? You salvage some soggy charts and want to know where you are. Both GPS have failed and so have the radios and the loss of the calculator means you can only do sums the hard way. Fortunately, you still have the sextant and this bone-dry and handy tome, which you previously sealed in polythene for just such an occasion.

This book is designed to enable the navigator to understand the issues associated with finding position by astronomy at sea and to be able to plot that position using appropriate sextant observations of celestial bodies with observations of time. The forms and the tables have been compiled to make the calculations straightforward, even without a calculator. However, as with all things practical, the best way to become competent is to practise.

Now read on...

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Catalogue Information

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