Today, while closing my windows before I turned in for the night, I realised the night sky was clear and cloudless and a distinctive formation of four bright stars caught my eye. Three of them were in a straight line, and the fourth and brightest was well-aligned with the centre star. Needless to say, curiosity took over, and Today QiYun Learnt that he was looking at a part of Cygnus, the Swan of the north (also called the Northern Cross). Without further ado...
Navigating with Cygnus
(The "Today QiYun Learnt" Digest: Celestial Navigation Series)
The Legend of Cygnus
First, let me tell you a story about the swan Cygnus. There are many legends, so the one I am telling you here is but one of them.
There were once two Greek gods: Cycnus and Phaeton (son of Apollo),who were best friends. One day, they decided to have a race. Being too focused on the race, they did not pay attention to where they were going and flew too close to the sun. Under the intense heat, their chariots began to catch on fire, and the two friends fell to the Earth. Cycnus crashed through some trees, breaking his fall. Phaeton landed in a river and was knocked unconscious. Cycnus wanted to rescue Phaeton, but he could not swim. He asked Zeus to turn him into a swan, so that as a swan, he could dive to the bottom of the river and save his good friend. Moved by the young man’s friendship, Zeus turned him into a swan named Cygnus. He dove to the bottom of the river and saved his friend’s life. However, as he was a swan, he could only live as long as a swan could live. So when he died, Zeus was again moved by his bravery and sacrifice, and placed him in the sky to serve as a reminder of courage and friendship.
Thus till today, in the Summer night skies, Cygnus can be seen diving to the bottom of the river, bravely rescuing his dear friend.
With this story in mind, one has a better idea of what orientation the constellation Cygnus takes, allowing oneself to orientate to its constituent stars and find one's position and heading. Which brings me to the next part: navigation using this constellation.
Navigation
Cygnus contains a number of stars that form a distinct cross-like structure in the Northern hemisphere. It is no surprise that this is named "the Northern Cross". The Northern Cross enables one to find Polaris and/or estimate North.
To find the Cross, look first for a star grouping known as the Summer Triangle, the corners of which are formed by three prominent stars--Vega, Deneb, and Altair.
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| Finding Polaris through Cygnus |
Vega is the triangle's leading star, and when high in the sky forms an east-west line with Deneb, the triangle's trailing star. This east-west line is of itself a good direction finder. Altair forms the Summer Triangle's southern corner.
Deneb forms the head of the Northern Cross. To find Polaris by the Northern Cross, start at Gienah--the star forming the end of the cross's trailing arm. Imagine a line extending from Gienah through Deneb at the head of the cross, and continuing straight out for about five times the distance between Gienah and Deneb. This line ends at Polaris.
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