Monthly Archives: August 2012

How To Locate The Pole Star (Polaris)

Posted on August 29, 2012 by Jack Case

First step – Look in the northern sky to find the constellation Ursa Major which is otherwise known as the Great Bear. Second step – find the Big Dipper (marked in red) which consists of the seven brightest stars of the constellation … Continue reading →

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The Southern Cross

Posted on August 29, 2012 by Jack Case

Just as we can use the Pole Star in the northern hemisphere to find the direction of north, we can use the Southern Cross in the southern hemisphere to find the direction of south.   However, whereas we can use the … Continue reading →

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The Rhumb Line

Posted on August 29, 2012 by Jack Case

If a ship were to steer a steady course, that is one on which her heading remains constant, her track would cut all meridians at the same angle, as the following diagram shows.  Such a line on the Earth’s surface … Continue reading →

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The Relationship Between Longitude, Latitude and the Nautical Mile.

Posted on August 29, 2012 by Jack Case

The Relationship Between Longitude and the Nautical Mile.  The Earth’s equatorial circumference is 21640.6 n.m.  Since the Equator is a great circle, 1o will subtend an arc of:  21640.6 ÷ 360 =  60.113  ≈ 60 n.m. There are 360 meridians of Longitude so … Continue reading →

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Calculating the Sun’s Declination in a Survival Situation

Posted on August 16, 2012 by Jack Case

In an ideal situation, we could find our latitude by using a satellite navigation system.  If sat-nav is not available, we can use astro navigation to calculate our latitude by the method shown at the following links: Latitude from the … Continue reading →

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