# Celestial Navigation in the GPS Age

Paradise Cay Publications, 2007 - Science - 274 pages
Many books on celestial navigation take shortcuts in explaining concepts; incorrect diagrams and discussion are often used for the sake of moving the student along quickly. This book tells the true story-and the whole story. It conveys celestial navigation concepts clearly and in the shortest possible time.It's tailored for navigation in the GPS age-a time of computers, calculators, and web resources. Although it covers all of the traditional methods of 'working a sight, ' the primary thrust is using the (under \$10) scientific calculator. By using equations that you key into your calculator, this book guides you toward a better understanding of the concepts of celestial navigation.You will learn novel ways to plot lines of position, ways to check your sextant accurately by star sights, and how to tell what time it is from a moon sight. The many appendices are a treasure of references and explanations of abstract ideas. Celestial Navigation is a crucial skill for the offshore navigator to know, this book provides the shortest path to that knowledge.

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### Contents

 INTRODUCTION 1 The Story Retold 2 The Fundamental Idea 3 The Key Concept 5 The Mariners Angle 6 The EqualAltitude Line of Position 7 The Limitations of Mechanical Methods 10 The Only Solution 12
 Other Lunars 97 THE ALTITUDE OBSERVATIONS 99 The Sextant 100 The Telescope 102 Telescopes with Traditional Horizon Mirrors 105 Sextant Checks and Adjustments 109 The Index Mirror 110 The Horizon Mirror 112

 PLOTTING THE CELESTIAL NAVIGATION LOP 13 Coordinates 14 The Navigation Triangle 16 The Local Hour Angle 18 Azimuth Angle and Azimuth 19 Three Plotting Methods 20 THE ST HILAIRE METHOD 25 The Straight Line Approximation 27 The Error 28 Why St Hilaire? 30 THE NAUTICAL ALMANACAN OVERVIEW 31 The Altitude Corrections 32 SUN SIGHT REDUCTIONS 35 Using Direct Computation 37 Altitude Corrections 39 The GHA and Declination Increments 40 The LHA 41 The Triangle Solution 42 Using Tables 44 The Solution Using HO249 45 The Solution Using HO229 48 Four Examples of Sun Sights 49 SIGHTS OF OTHER CELESTIAL BODIES 55 The Planets 57 The Stars 59 Star Sights by Direct Calculation 60 Star Sights by HO249 62 The Moon 63 SPECIAL SIGHTS 67 Meridian Sights 69 Latitude without Meridian Shots or UT 70 Latitude and Longitude from Meridian Sights 71 Longitude from Altitude and Latitude 73 Position without St Hilaire 77 LUNAR DISTANCE SIGHTS 81 Taking the Lunar Sight 83 The Distance Clearing Concept 85 Clearing the Lunar Distance 88 The Sight Reduction 90 A Lunar Example 94 Accuracy 95 So Why Lunars Today? 96
 Index Error 113 Backlash 114 Sextant Arc Error 115 Taking a Sight 117 Averaging Sights 121 Altitude Corrections 124 Refraction 125 Parallax 126 OPERATIONS AT SEA 129 Celestial with GPS 130 Those Special Sights 133 Plotting 134 Estimated Positions and Running Fixes 135 Special LOP Orientations 138 Great Circle Sailings 141 Time 143 Accuracy 144 TABLES CALCULATORS AND COMPUTERS THE DEBATE 147 Calculators and Computers 151 INSIGHTS FROM THE NAVIGATION TRIANGLE 155 The Azimuth Rules 158 Special Cases of the Azimuth Equation 160 EXERCISES FOR UNDERSTANDING AND CONFIDENCE 163 Sight Reduction and the Navigation Triangle 165 Navigational Astronomy 175 Courses Distances and Charts 181 Lunar Distances 185 Computer Programming 189 APPENDICES 195 APPENDIX A NAVIGATION TRIANGLE FORMULAE 196 APPENDIX B CALCULATOR KEYSTROKES 200 APPENDIX C EXCERPTS FROM THE NAUTICAL ALMANAC 207 EXCERPTS FROM HO229 216 SIGHT REDUCTION WORKSHEETS 230 APPENDIX F CONCEPTS IN PLANE GEOMETRY 237 APPENDIX G SEXTANT ARC ERROR TABLES 239 APPENDIX H DIP SHORT OF HORIZON 253 APPENDIX I A BRIEF HISTORY OF NAVIGATION 254 APPENDIX J ANNOTATED BIBLIOGRAPHY 260 ABBREVIATIONS USED IN THE TEXT 265 INDEX 267 Copyright

### About the author (2007)

John Karl is a physicist, artist, pilot, writer, and a sailor. He learned celestial navigation 50 years ago and has been sailing for 60 years. He's taught celestial navigation workshops at the Univesity of Wisconsin and aboard the 3-masted S/V Denis Sullivan, conducted marine research in the Great Lakes and Gul of California.