Of Degrees and the Summer Triangle

Ever wondered how to measure "distances" in the sky? Astronomers use the units of degrees to measure the separation in arc-distance from one object to another. Interestingly, the human hand and arm work nicely to allow you to measure degrees. One fist width placed out at arm’s length is about 10 degrees of arc. Spreading your thumb and pinky fingers apart (aka the Hang Loose hand) gives you about 20 degrees. One degree is about the width of your pinky finger’s nail. There are a number of web sites which can show you more about this method. Here’s one: http://www.abc.net.au/science/articles/2009/07/27/3169109.htm

Written for those in the northern hemisphere:

Now you can go out and find the Summer Triangle, a familiar asterism of three bright summer constellation stars: Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila).  At about 11:00 PM local time, if you look to the east, you will note three pretty bright stars which make a big triangle in the sky. The highest one off of the horizon is Vega in the constellation of Lyra, the lyre or harp. It appears as a pretty bright blue-white star.

About 24 degrees to the lower left (moving down to the eastern horizon) is the star Deneb in the constellation of Cygnus the swan. This star appears to be about the same color as Vega, and to my eyes perhaps a little less blue.

38 degrees to the lower right of Deneb, and 34 degrees to the lower right of Vega is our third star, Altair in the constellation of Aquila the eagle. This is the lowest star in the triangle, and the one furthest to the south.

There! You’ve just found the Summer Triangle! You also have learned the skill which will allow you to chart the entire sky (should you want to take on that venture). Enjoy the night!

About johnb

- Director of Grainger Observatory, Phillips Exeter Academy. - Variable-star-crazed astronomer, but have done research in other areas. - Drummer, archer, pilot, chef, friend, pet owner, husband, father, Train-nut.
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