Celestial Navigation in the GPS Age

311 Pages·2012·11.38 MB·English

by  Karl

CELESTIAL
NAVIGATION
IN THE GPS AGE
REVISED AND EXPANDED
John Karl
Copyright ©2007, 2009, 2011 John H. Karl All rights reserved. No part of this book may be used or
reproduced in any manner whatsoever without written permission, except in the case of brief quotations
embedded in critical articles and reviews. For information, contact the publisher.
Nautical Almanac data is reproduced with permission from Her Majesty's Nautical Almanac Office, ©
CCLRC 2004. CCLRC is an abbreviation for Council for the Central Laboratory of the Research Councils,
who own the copyright on the data.
No copyright claimed for sight reduction worksheets in Appendix E, pages 277-283.
Cover design by Rob Johnson, www.johnsondesign.org
Editing and book design by Linda Morehouse, www.webuildbooks.com
Revised edition editing by Rebecca S. Bender
Painting on inside front cover, oil on canvas, “Captain Sumner Discovers the Celestial Line of Position” by
John H. Karl Printed in the United States of America
First Edition, Third Printing
ISBN 978-0-939837-75-7
Published jointly by
Paradise Cay Publications, Inc. Celestaire, Inc.
P. O. Box 29 4609 E. Kellogg Drive
Arcata, CA 95518-0029 Wichita,KS 67218
[phone] [phone]
[phone] (Fax) [phone] (Fax)
www.paracay.com www.celestaire.com
[email protected] [email protected]
To Karen, shipmate in life
FOREWORD
Celestial navigation is seen today in a different light than before GPS became
affordable and ubiquitous. Yes, it is the only manual way to navigate at sea (and
one needs a manual way to do anything important at sea). But when celestial
navigation was required, it seemed like work. Now it can be fun. It frees us from
keys and menus that only serve to summon the expertise of some programmer
and lets us do something by ourselves—with our own two hands.
Today's navigator needs not be an expert anymore, but should know enough
to use celestial fixes as a backup. Of course he may take the study further, and
therein lies the enticement. Celestial navigation is easy to start, but can take time
and study to master. Activities like this have always held lasting fascination
(some would say addiction) for us.
John Karl's book lets the reader proceed in this way. A line of position is put
on a chart after only 40 pages. But then he will take you further in understanding
the science and art of celestial navigation than any other book I have seen.
Celestial Navigation in the GPS Age is a mixture of history, math, and rational
explanations that the reader may sample as desired.
This may not be the only book to which you are exposed in learning celestial
navigation, but it certainly should be one of them.
—Kenneth Gebhart
Kenneth Gebhart is the author of the Celestaire Navigation Catalog. He is well
known for his celestial navigation seminars given at most sailboat shows.
PREFACE
Browsing in a bookstore when I was about nine, I bought a book called
American Practical Navigator by someone I had never heard of—Nathaniel
Bowditch. I guess it caught my eye because I was interested in boating and
sailing. Wading through Bowditch was tough going at that age. I had never
heard of logarithms or haversines. But I did learn something about navigation
and astronomy, which, looking back, I think was responsible for leading me into
science.
After this encounter, Bowditch sat on my bookshelf for many years. Then
while studying physics at The Massachusetts Institute of Technology, I stumbled
upon a sextant in a pawn shop, bought it, and dragged out Bowditch again. This
time I understood a whole lot more about astronomy and mathematics. Living in
Marblehead made practice sights easy from the top of a hill near Red's Pond
where I could view the sea horizon. At that time, I practiced sight reductions
using the log-haversine method taught in Bowditch.
Much later during my sporadic 60-year sailing experience, and after retiring
from a physics career, I left Hawaii headed for San Francisco on a 34-foot cutter.
Having not sailed blue waters for some years, I discovered how very simple
sight reduction has become with a scientific hand calculator. Moreover, I
realized that all modern sight reductions are based on just one math formula,
expressed in two ways. How very simple modern methods have become.
Nonetheless, the practice of celestial navigation has changed little over two
hundred years, for navigators still use ancient tables of logarithms or trig
functions. Yet today, I can't imagine a scientist or engineer who, faced with
evaluating a simple trig expression, would reach for a set of tables rather than a
hand calculator. After all, handheld scientific calculators have been available for
over three decades and now cost under $10.
Recently I had the opportunity to teach celestial navigation aboard the three-
masted S/V Denis Sullivan on a leg from Milwaukee to Montreal. That
experience inspired me to write this book. My goal as a scientist and teacher is to
explain away the mystery of the subject in a simple fashion while covering the
fundamental concepts better than ever before. My goal as a sailor is to provide
the simplest possible sight reduction procedure that can be reliably and
comfortably used at sea, using either calculators or tables—that's a personal
choice. My tenet is that modern developments can be used to provide deeper
understanding and much broader applications of celestial navigation than the old
ways.
You and I will take a navigator's celestial journey that integrates the old with
the new, tables with calculators, celestial navigation with GPS. We'll assume no
mathematical sophistication. Rather, we'll first explain how anyone can easily do
the math as a series of instructions, perfunctorily punching designated calculator
buttons. Then we'll explain how the math relates to sight reduction tables, how to
use the tables, and their advantages and disadvantages. We'll not develop the
math; we'll explain it. It tells us everything. Listening to its simple story, we'll
gain deep insight that will stick with us long after the celestial voyage ends with
the rattle of the anchor chain. By understanding the mysteries of the heavens,
we'll rapidly arrive at a simple, cheap, memorable, and reliable sight reduction
procedure.
Please read with care, interest, and pleasure, and come away with a useful, if
unusual, skill.
–– John Karl, February 2007
PREFACE TO THE 2ND PRINTING
In addition to making minor corrections and improvements from the first
printing, I've adopted a more conventional notation for the azimuth angle from
true north, changing it from Az to Zn. Also, beyond these slight improvements,
the section on Polaris sights has been revised, and the sextant arc error tables in
Appendix G have been made more convenient.
–– John Karl, February 2009
PREFACE TO THE REVISED AND EXPANDED EDITION
My goal in writing this book has been to present an accurate, clear, and
comprehensive treatment of celestial navigation, while simultaneously enabling
the reader to work a sight reduction after reading only a few pages. This edition
now provides an even shorter and easier path to useful celestial navigation by
introducing simple tabular methods first. Then optional calculator methods
follow for those wishing to take full advantage of their flexibility.
The section on stars has been expanded to include a more complete treatment
of using H.O. 249 (UK's NP 303) for stars, which then leads into planning sights
of stars and planets, along with details on star-planet identification and viewing.
The chapter on special sights has been expanded to treat three different Polaris
sight reductions, speed corrections for meridian shots, and even obtaining LOPs
without a sextant. Chapter 10 now includes more discussions on constructing
plotting sheets; using universal plotting sheets; making three different kinds of
running fixes; performing compass deviation checks at sea; and using ocean
pilot charts for planning voyages.
Finally, in several places it was possible to improve the discussion by
making minor changes, adding more detail, and more figures.
–– John Karl, October 2010
ABOUT THE AUTHOR
John Karl is a physicist, artist, pilot, writer, and sailor. He learned celestial
navigation 50 years ago and has been sailing for 60 years. Karl has sailed the
Pacific Ocean, East Coast, Great Lakes, Florida Keys, and the Bahamas. He has
taught celestial navigation workshops at the University of Wisconsin and aboard
the 3-masted S/V Denis Sullivan. He has also conducted marine research in the
Great Lakes on the R/V Salmo and in the Gulf of California aboard the R/V
Melville.
ACKNOWLEDGMENTS
It's a pleasure to gratefully thank my son, John, for his critique of early
versions of the manuscript; Michael Briley for providing proper-motion star
data; James McKee for his helpful and productive review of the manuscript; and
my two publishers for their commitment to celestial navigation.
I'm also very appreciative of the time and effort of Stan Klein, Geoffrey
Kolbe, and Steve Whiteside in reviewing the book and suggesting valuable
changes and corrections for the 2nd printing. George Huxtable not only was very
helpful suggesting corrections, but also helped me improve the way stellar
aberrations are handled in Appendix G.