Tag Archives: navigation

The Importance Of Morning And Evening Star Sights

Part 1 – Checking to see which stars and planets will be above the observer’s horizon during Nautical Twilight on a certain day. By Jack Case Introduction. The Astronomical Position Line.  A position line is a line drawn on a … Continue reading

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Stars For All Seasons Part 6

Winter Stars in the Northern Hemisphere “Know The Stars And You Will Always Have A Compass”.    (Michael Punk. 2002. The Revenant)   As we move into winter, new constellations take their place in the night sky of the northern hemisphere … Continue reading

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Stars For All Seasons Part 4

Circumpolar Stars In The Southern Hemisphere. In the previous article of this series, we discussed circumpolar stars of the Northern Hemisphere and  in this article we will look at some of the circumpolar constellations in the Southern Hemisphere. Centaurus is the … Continue reading

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Stars For All Seasons – Part 2

Summer Stars in the Northern Hemisphere  Winter Stars in the Southern Hemisphere “Know The Stars And You Will Always Have A Compass”.    (Michael Punk. 2002. The Revenant) In the last article, we discussed Rotation (the reason the stars seem to rise … Continue reading

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In Defence of Mer Pas

The noon sight for latitude is a method of calculating latitude from the altitude of the sun at the instant it crosses your meridian and for this reason, the method is also known as ‘Meridian Passage’ or ‘Mer. Pas’.  I … Continue reading

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Why Astro?

In a recent article the discussion centred on our over-reliance on GPS for navigation at sea and the need for back-up systems.  The conclusion drawn was that we already have a back-up system, one that has been tried and tested … Continue reading

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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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The Importance of Azimuth and Altitude in Astro Navigation

 In the diagram above, the celestial sphere is drawn in the plane of the observer’s meridian with the observer’s zenith (Z) at the top.  Point O represents both the observer and the Earth. Z represents the observer’s zenith. X is … Continue reading

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Bearing, Azimuth and Azimuth Angle.

For students of astro navigation, the various definitions of azimuth, azimuth angle and bearing can cause much confusion. It is hoped that the following will help to clarify this topic. Bearing is the direction of something in relation to a … Continue reading

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A Plan Of Mathematical Perfection. (Learning from the Polynesians)

In the two previous posts of this series, we focussed on astro navigation aspects of the ancient voyaging techniques of the Polynesians and the Micronesians.  Because of that narrow focus, we did not do justice to the abounding knowledge and … Continue reading

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