Star Markers

StarDate: May 20, 2011

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There's not much need for celestial navigation these days. It's far easier to find your way with GPS. Even so, using the heavens to learn something about your location is still a fun exercise for an evening under the stars.

The most famous celestial marker is the North Star, Polaris. It stands due north every night of the year, anchoring the sky as the other stars wheel around it.

Polaris's altitude above the horizon tells you your latitude. From here in Austin, for example, Polaris stands 30 degrees up -- one-third of the way up the sky -- which tells us that Austin is at 30 degrees north latitude. If Polaris is half way up the sky, then you're at 45 degrees north -- the latitude of Minneapolis.

Another marker is Cassiopeia, the queen, whose brightest stars form a letter W. The top points of the "W" are just about 30 degrees from Polaris, so Cassiopeia's position as it wheels below Polaris is another good latitude marker.

Tonight, it stands due north as the sky gets dark. But how much of it you see depends on your latitude. From Austin, the two stars at the top left and top center points of the "W" just skim the horizon. They're so low, though, that even with a clear horizon you can't see them through the thick layer of air.

From the latitude of Kansas City, the entire letter stands just atop the horizon. And from Seattle, there's plenty of room between the letter and the horizon -- a celestial hint that you're pretty far north.

 

Script by Damond Benningfield, Copyright 2011

 

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