Introduction to Celestial Navigation

Frontmatter

Chapter 1. Introducing the Celestial Sphere

Abstract

To an observer on the Earth, the sky has the appearance of an inverted bowl, in the sense that the stars and other heavenly bodies, irrespective of their actual distance from the Earth, appear to be situated on the inside of a sphere of immense radius described about the Earth as centre.

Alexander Arnfinn Olsen

Chapter 2. Time Systems

Abstract

The world is divided into 24 standard time zones. The term ‘standard time zone’ is the generic term for all time zones within the ‘Uniform Time System’, both on land and at sea. Each zone is 15° wide, with each zone numbered and lettered.

Alexander Arnfinn Olsen

Chapter 3. Practical Sights: Planning, Taking, Reducing and Plotting

Abstract

This chapter provides a practical guide for planning, taking, reducing and plotting of celestial sights for readers studying towards their Certificate of Competency (CoC) for merchant seafarers or the Navigational Watchkeeping Certificate (NWC) for Naval cadets, or indeed any other national equivalent which meets the standards set out under SOLAS. This chapter uses NAVPAC 4 as the primary point of reference and can be worked through, step by step, with the instructions provided throughout the chapter; it is not intended that the NAVPAC elements of this chapter should be read in isolation. Given this chapter is based on NAVPAC v.4.0.12, incremental releases/updates may have marginally different functionality. Previous versions of NAVPAC (such as NAVPAC 3.4 (as supplied on the DP330 CD) contains the same almanac data and so will produce the same results but has less additional capability and does not benefit from the improved user interface. Newer versions of NAPVPAC should produce the same results though the user interface will likely be different.

Alexander Arnfinn Olsen

Chapter 4. Observing Celestial Sights Using an Artificial Horizon

Abstract

In certain circumstances, the horizon may not be visible, and thus traditional methods of taking observations will not be possible. When observing from a static position (i.e., not a rolling and pitching ship), it is possible to use the artificial horizon or ‘syrup’ method to take Sun sights.

Alexander Arnfinn Olsen

Chapter 5. Identification of Heavenly Bodies

Abstract

The methods for identifying heavenly bodies were covered previously in Chaps. 1 and 4.

Alexander Arnfinn Olsen

Chapter 6. Meridian Passage and Polaris

Abstract

The ‘meridian passage’ of a heavenly body occurs when it is in the observer’s meridian or in the meridian 180° from the observer’s meridian. At that moment, the local hour angle of the heavenly body will be either 0° or 180°, and the heavenly body is either due North or due South (i.e., bearing 180° or 000°) from the observer. The position line obtained, being at right-angles to the bearing, will instantly give the observer’s latitude. Although sights can be taken for the meridian passage of any heavenly body, it is normally only observed for the Sun. Occasionally, Jupiter and Venus may also be usefully observed by day.

Alexander Arnfinn Olsen

Chapter 7. Rising and Setting of Heavenly Bodies

Abstract

A thorough understanding of the rising and setting of heavenly bodies is essential for ship’s navigators. This is not only in order to plan the time at which star sights may be taken, but more importantly, for planning operations which require total darkness, twilight or moonlight. Today, a number of sources of this information are available, but it remains essential that specialist navigators understand the theory and are able to complete the calculations manually.

Alexander Arnfinn Olsen

Chapter 8. Refraction, Dip and Mirage

Abstract

Light, or other wave energy, is assumed to travel in a straight line at uniform speed, provided the medium through which it is travelling has uniform properties. Thus, the speed of light in a vacuum is ‘c,’ but a light ray travelling through water will travel at an appreciably lower velocity, and in some peculiar forms of matter it is possible for light to travel at only a few meters per second.

Alexander Arnfinn Olsen

Chapter 9. Errors in Celestial Position Lines

Alexander Arnfinn Olsen

Chapter 10. Sky at Night

Abstract

The 58 ‘navigational stars’ are illustrated in Fig. 10.1. The red line indicates the most convenient route for identifying one star from another, if observing them without instruments.

Alexander Arnfinn Olsen

Chapter 11. Hour Angles

Abstract

Hour angles and their specific variants were introduced in Chap. 18 but may be defined more precisely as follows.

Alexander Arnfinn Olsen

Chapter 12. Theory of Time

Alexander Arnfinn Olsen

Chapter 13. Plane Trigonometry

Abstract

Trigonometry is the branch of mathematics dealing with the relations between the angles and sides of a triangle and with the relevant functions of any angles. This chapter contains the following information, though for full details, consult an appropriate textbook.

Alexander Arnfinn Olsen

Chapter 14. Spherical Trigonometry

Alexander Arnfinn Olsen

Chapter 15. The Spherical Earth

Abstract

This chapter touches on the following subject areas: Meridional parts for the sphere. Construction of the meridional parts formula for the sphere. Evaluation of the meridional parts formula for the sphere. Corrected mean latitude for the sphere.

Alexander Arnfinn Olsen

Chapter 16. Projections

Abstract

Conical orthomorphic projection on the sphere.

Alexander Arnfinn Olsen

Chapter 17. The Spheroidal Earth

abstract

In this chapter, we will look at the following.

Alexander Arnfinn Olsen

Chapter 18. Vertical Sextant Angles

Abstract

This chapter contains additional information for the use of vertical sextant angles in fixing.

Alexander Arnfinn Olsen

Chapter 19. Doubling the Angle on the Bow

Abstract

This chapter contains instructions for ‘doubling the angle on the bow’ and the effect of current and/or tidal stream on this technique.

Alexander Arnfinn Olsen

Chapter 20. Errors in Terrestrial Position Lines

Abstract

In this chapter touches on the following subject areas.

Alexander Arnfinn Olsen

Chapter 21. Paper Charts and Chartwork

Abstract

This chapter contains the techniques and procedures to be used when navigating on paper charts, including the symbols to use. These were the standard procedures used when paper charts were the standard (and only) means of navigating at sea.

Alexander Arnfinn Olsen

Backmatter