Category Archives: astronomy

Venus Evening Star or Morning Star?

Posted on April 25, 2020 by Jack Case

Venus sometimes appears as an evening star above the western horizon shortly after sunset and sometimes appears as a morning star above the eastern horizon shortly before sunrise.  In primitive times, people regarded the evening and morning stars as two … Continue reading →

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The Retrograde and Prograde Motions of Mars and Jupiter

Posted on September 15, 2019 by Jack Case

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

Posted on September 6, 2019 by Jack Case

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

Posted on June 19, 2019 by Jack Case

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

Posted on May 11, 2019 by Jack Case

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

Posted on March 25, 2019 by Jack Case

The ‘Where To Look’ Method. Devised by Jack Case                          HOME In part 1 of this series, we discussed how we can establish whether or not a selected star  … Continue reading →

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The Importance Of Morning And Evening Star Sights

Posted on February 19, 2019 by Jack Case

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

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Stars For All Seasons Part 6

Posted on December 12, 2018 by Jack Case

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 5

Posted on November 16, 2018 by Jack Case

Autumn Stars in the Northern Hemisphere Spring Stars in the Southern Hemisphere.   During early autumn in the northern hemisphere, as the Earth continues to orbit the Sun, the last of the summer stars such as Altair, Vego, Deneb, Nunki … Continue reading →

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Stars For All Seasons Part 4

Posted on October 16, 2018 by Jack Case

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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