Category Archives: navigation

The Retrograde and Prograde Motions of Mars and Jupiter

Mars We can best understand  the retrograde and prograde motions of Mars by considering the planet’s motion relevant to distant stars.  To do this, we must study the effect of the motions of both the Earth and Mars around the … Continue reading

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Making An Ocean Plotting Sheet

Ocean plotting sheets are nautical charts designed for use at specific latitudes. They are used for ocean navigation where features such as shorelines, water depths and local tidal information are of no importance. Plotting sheets are particularly useful for plotting … Continue reading

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The Purpose of Altitude and Azimuth Angle in Position Finding at Sea

To fully understand how the azimuth angle and the altitude of a celestial body help us to establish our position, we need to consider them in relation to the celestial sphere. Consider the diagram below: The celestial sphere is drawn … Continue reading

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Planning Star and Planet Sights

Fixes from Sightings of Stars and Planets.  There are 59 navigational stars and 4 navigational planets which we can use to achieve position fixes. However, there are only two short periods during the day in which we can do this … Continue reading

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The Importance of Morning and Evening Star Sights – Part 2

The ‘Where To Look’ Method. Devised by Jack Case In part 1 of this series, we discussed how we can establish whether or not a selected star  or planet will be visible during nautical twilight.  In this post, we discuss … Continue reading

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Stars For All Seasons Part 7 – Spring Stars in the Northern Hemisphere.

Spring Stars in the Northern Hemisphere. Spring is just around the corner and when the winter constellations begin to make their exits to the west, we will find Boötes, Leo, Cancer, Hydra and Virgo lurking in the wings ready to … 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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Accuracy of Sight Reduction Methods.

In my recent article ‘Why Astro‘, I highlighted the risks in using the GPS.  Since writing that article, I am frequently asked “if astro / celestial navigation is to be used, which of the many systems is the best”.  Sight … 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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