Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Thursday, February 20, 2014

Locating the North Star

This fine post is from my local news paper The Bend Bulletin.  Written by Ken Fair Field; nice work.

Learn how to find Polaris in night sky
Published Feb 19, 2014 at 12:06AM / Updated Feb 19, 2014 at 06:41AM
In an age of seemingly magical electronic devices, GPS being one, we rely on technology to determine where we are on the planet, enabling us to navigate at sea, along the ground and in the air. Still, it is comforting to know that in the absence of technical aids, it remains possible to tell directions and know by latitude where we are on the planet.
Long ago, travelers used the North Star, Polaris, as a reliable tool to navigate safely over long distances. With a few guideposts in the night sky, you can find the North Star without a telescope or sky chart.
The Big Dipper is located in the lower portion of the constellation Ursa Major. At 8 p.m. tonight, it will be high in the sky over the northern horizon (see illustration). Four stars form its “bowl” with three more making up its attached “handle.”
By naked eye, find the two outside “bowl” stars, Dubhe, the lower star, and Merak, the upper one. Less light-polluted areas make spotting them easier. Draw an extended imaginary line through the outside “bowl” stars, and the line will lead you to the North Star. Polaris is the end “handle” star of the Little Dipper, which is inverted in relation to the Big Dipper. Facing Polaris points you north. South will be directly behind you. West will be at your left hand and east at your right. You have identified the four directions!
Now, extend an imaginary line from yourself to the horizon below Polaris. Still looking at Polaris, draw a straight line angling from Polaris to you. The angle created at the intersection of these two lines (your position) reveals your latitude on Earth, about 44 degrees. To further illustrate, if you were at the North Pole, Polaris would be directly over your head, making an angle of 90 degrees.
Stars appear to move in circles around Polaris at the rate of about 15 degrees every hour to complete a full circle. In reality, of course, this illusion is created because the Earth rotates west to east. Place a camera on the ground and leave its shutter open for a while and the image obtained will show beautifully curved star trails representing portions of complete circles.
— Kent Fairfield is a volunteer with Pine Mountain Observatory and a lifelong amateur astronomer. He can be reached at Other PMO volunteers also contributed to this article.

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