Category Archives: Astro Navigation Demystified

Calculating Changes in Longitude and Time Along a Parallel of Latitude.

If two ships are both positioned exactly on the Equator but are separated by 900 nautical miles in an east/west direction, then in terms of longitude, they will be 15o apart and in terms of Greenwich Mean Time, they will be … Continue reading

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Pillars of the Sky (Learning from the Polynesians).

The last post in this series discussed the Polynesian’s Star Compass and their use of ‘steering stars’ for direction finding.  Although the Polynesians made extensive use of a form of dead reckoning to estimate position, as far as we know, … Continue reading

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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 2.

Part 2 – The Intercept Method Link:  Astro Navigation In A Nutshell Part One Suppose we are in a yacht and we measure the altitude of the Sun and find it to be 35o; what does this tell us?  All … 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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The Demystified Astro Navigation Course – Unit 4

Unit 4 – The Importance of Altitude, Azimuth and Zenith Distance in Astro Navigation.  Zenith. The Zenith is an imaginary point on the celestial sphere directly above the observer.  It is the point where a straight line drawn from the … Continue reading

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The Demystified Astro Navigation Course – Unit 3 Part 1

Unit 3  Part 1 – Altitude and Azimuth     The Azimuth is similar to the bearing in that it is the angle between the observer’s meridian and the direction of the celestial body.  However, whereas bearings are measured clockwise from north … Continue reading

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Finding Stars and Constellations, Part IV

This post continues the series Finding Stars and Constellations.     Boötes  The Herdsman   If we take a line from Alioth to Alkaid in the Great Bear and extend that line in an -imaginary curve for about roughly three hand-spans … Continue reading

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