Star Trails

I stumbled on a Wikipedia page dedicated to star trails that I found fascinating and beautiful.

Star Trails

Star Trails shot from the International Space Station

Wikipedia defines star trails as: “A type of photograph that utilizes long-exposure times to capture the apparent motion of stars in the night sky due to the rotation of the Earth. A star trail photograph shows individual stars as streaks across the image, with longer exposures resulting in longer streaks. Typical exposure times for a star trail range from 15 minutes to several hours…”

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Moonset

However, star trails don’t have to be images of stars (as you can see in the moon trail image above). Also, they don’t necessarily require rotation of the earth. They can be obtained by rotating the camera or following the motion of something else (like a comet). Finally, with the advent of digital cameras, it has become possible to get the same effect by taking multiple short exposure shots and “stacking” them in imaging software, like Photoshop.

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In the center of this image is the star, Polaris

 

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Boge-Rugove (3 hours of earth rotation), by Bleron Caka

The closer you are to either pole, the tighter the star trail circles become. The closer you are to the equator, the broader the trail’s arc. When you view star trails in the northern hemisphere, the trails are centered around the North Celestial Pole. In the heart of those northern star trails is Polaris, the North Star.

However, because the Earth’s rotational axis wobbles like a spinning top, Polaris has not always been near the North Celestial Pole. In fact, 6,000 years ago, the North Star was off of true north by about 30 degrees!

And there, mes amis, is the deft tie-in to history.

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