I am delighted to have been invited to write the Foreword to this collaborative publication by the Royal Navy and The Nautical Institute, which builds on earlier work to make the authoritative 'Admiralty Manuals of Navigation' available to a much wider readership.
Although the maritime community relies heavily on GPS or its GNSS equivalents for everyday use, all mariners should be able to use non-satellite methods of navigation to cover the eventuality of satellite loss, equipment or aerial defects, and accidental or hostile GPS interference or jamming. For oceanic areas this means that astro navigation skills are essential for the majority of mariners.
There are three great obstacles to conducting successful astro navigation. The first is the manual skill needed to use a sextant accurately, especially in difficult conditions; this can only be acquired by regular practice. A reasonably skilful sextant operator should be able to obtain four star sights with a fix accuracy of ± Vi nautical mile in good conditions. The second is the complexity of the calculations needed to obtain a result. The third is the time necessary for astro navigation if manual calculation methods are used. These latter two obstacles can be a disincentive to practising with a sextant altogether.
However, with the advent of the United Kingdom Hydrographic Office's 'NAVPAC software, developed by HM Nautical Almanac Office, all the labour and complexity of calculation has been reduced to inputting the heavenly bodies' names, their sextant angles and times of observation into the software on a desktop PC or a laptop. Instantly, the software calculates the position lines, plots them, calculates a fix position and remembers it for later use, so that a full passage plan can be executed, fix-by-fix and day-by-day. Not surprisingly, the Royal Navy has adopted this software as its primary method of conducting astro navigation. With this labour and time saving tool, there is no excuse for not practising one's skills with a sextant and gaining the necessary dexterity needed.
To complement HM Nautical Almanac Office's software achievement, this book provides very clear and concise guidance for astro navigation, suitable for both the novice and the expert. The first three chapters provide a simple 'how to do it guide', mainly based around 'NAVPAC and practical guidance on how best to use a sextant, while the rest of the book deals with the deep theory and other calculation methods.
Practice in merchant ships has been to use a variety of specially configured hand-held calculators to reduce sight observations. This volume still covers the application of this method, together with manual calculations, while concentrating on 'NAVPAC.
With its comprehensive cover of various methods of calculation, this volume is equally applicable to yachtsmen and merchant ships operating out of sight of land, all of whom need a reliable alternative to GPS. Armed with this authoritative manual, 'in date' practical skills in astro navigation can once again be the stock-in-trade of every mariner, in the event that GPS or its GNSS equivalents should fail or become unavailable, either through accident or hostile act.
Книга полность на английском языке, является продолжением Admiralty Manual of Navigation Volume I
Chapter 1 The Celestial Sphere - Introduction
Section 1 Basic Definitions and Structure
Section 2 The Magnitudes of Stars and Planets
Section 3 Methods of Identifying Heavenly Bodies
Chapter 2 Time Systems
Chapter 3 Practical Sights: Planning, Taking, Reducing and Plotting
Section 1 Scope, Assumptions and Software
Section 2 Planning Astro Sights
Section 3 Description, Preparation and Use of Sextants
Section 4 Reducing Sights (Processing of Sextant Readings)
Section 5 Plotting Sights
Annex ЗА Observing Astro Sights Using an Artificial Horizon
Chapter 4 The Celestial Sphere - Definitions, Hour Angles and the Theory of Time
Section 1 Glossary of Definitions
Section 2 Hour Angles
Section 3 Solar Time
Section 4 Sidereal Time
Section 5 Lunar and Planetary Time
Section 6 Parallax and Horizontal Parallax
Chapter 5 Identification of Heavenly Bodies, Astronomical Position Lines, Observed Position and Sight Reduction Procedures
Section 1 Identification of Heavenly Bodies
Section 2 Astronomical Position Lines
Section 3 Calculating Altitude, Azimuth and True Bearing
Section 4 Sight Reduction Procedures and Methods
Section 5 Very High Altitude (Tropical) Sights
Section 6 High Latitude (Polar) Sights
Annex 5A Description and Setting of the Star Globe
Chapter 6 Meridian Passage and Polaris
Section 1 Meridian Passage
Section 2 Polaris
Chapter 7 The Rising and Setting of Heavenly Bodies
Section 1 Requirements and Generic Definitions
Section 2 Sunrise, Sunset and Twilights
Section 3 Moonrise and Moonset
Section 4 High Latitudes
Chapter 8 Refraction, Dip and Mirage
Chapter 9 Errors in Astronomical Position Lines
Appendix 1 The Sky at Night
Appendix 2 Extracts from The Nautical Almanac (1997)