Tag Archives: navigation

The Polynesian Star Compass (Learning from the Polynesians)

Updated version. “Know the stars and you will always have a compass”  (The Revenant) * Nainoa Thompson tells us how that, for centuries before European sailors reached the Pacific Ocean, the South Sea Islanders accurately found their way from island … Continue reading

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Astro Navigation In A Nutshell Part Four

Part 4 – Full procedure for establishing an astronomical position line. This post brings together all of the information from parts 1, 2 and 3 of this series to demonstrate the full procedure for establishing an astronomical position line. .Links:  Astro … Continue reading

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Astro Navigation In A Nutshell Part 1

Links Astro Navigation in a Nutshell Part 2 Astro Navigation in a Nutshell Part 3 Astro Navigation in a Nutshell Part 4 Part 1 – The Importance of Azimuth and Altitude.  The theory of astro navigation depends on the ability … Continue reading

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Astro Navigation In A Nutshell Part 2.

Part 2 – The Intercept Method Link:  Astro Navigation In A Nutshell Part One Astro Navigation in a Nutshell Part 3 Astro Navigation in a Nutshell Part 4 Suppose we are in a yacht and we measure the altitude of … Continue reading

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Astro Navigation in a Nutshell Part 3

Part 3 – Calculating Altitude and Azimuth at the Assumed Position by Spherical Trigonometry. Links:  Astro Navigation In A Nutshell Part One Astro Navigation In A Nutshell Part Two Astro Navigation in a Nutshell Part 3 Astro Navigation in a Nutshell … Continue reading

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Applying the Equation of Time when calculating longitude at the Sun’s Meridian Passage.

Author’s Note:  The original issue of this post was found to contain errors which have now been corrected.  Many thanks to Jeremy Parker for bringing the errors to my attention. Although the imaginary Mean Time gives us an accurate measurement … Continue reading

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Short Distance Sailing And Rhumb Line Sailing

In my previous post about the meridian passage long method, I demonstrated how the ‘Short Distance Sailing Formulas’ are used to calculate a vessel’s position at meridian passage.  I have since received several questions asking how these formulas allow for … Continue reading

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Meridian Passage Long Method

Links:  Understanding Meridian Passage, Equation of Time,   Meridian Passage Short Method,  Short Distance Sailing Formulae,  What is the point of meridian passage?         Zone Time,    Local Hour Angle and Greenwich Hour Angle,   Converting GMT to GHA … Continue reading

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Understanding Meridian Passage (Mer Pas)

Meridian Passage occurs when a celestial body crosses the observer’s meridian of longitude and at that instant, it will reach its greatest altitude above the observer’s horizon. The following diagrams will help to explain how the latitude can be calculated from the … Continue reading

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Altitude Corrections For The Moon

Continuing the series on the Moon. When a navigator measures the altitude of the Moon, there are several corrections that he has to make to the readings. Corrections For The Moon’s Semi-Diameter.  The point on the Moon’s circumference nearest to … Continue reading

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