Benifits of Looking for Double Stars

Searching for double stars has a benefit…….. it teaches you something about resolving power which is the ability of your telescope to give you a detailed image of an object. When you look at a double star in your telescope, you are going to find out quickly how your telescope will handle two objects which are closely spaced together in the sky.

Double Star (Click To Enlarge)

Double Star (Click To Enlarge)

By looking at double or triple star systems you also can develop your skill in determining the stellar magnitude of these stars. As the pair of stars in a double star system will most likely differ greatly in magnitude, you should be able to quickly tell which of the two is the brightest. Then before long you can look at the stars and visually notice that a star may just have gone from magnitude 2 to 3 for example…. which means that the star is now 2.5 times fainter than it was before.

Observing double stars will also show you how stars appear in different conditions….. and is therefore a good way to determine seeing conditions for the night.If you are looking at these double stars and you can see them twinkle, then you have what is known as stellar scintillation where you are viewing the stars through thick layers of turbulent moving air in the Earth’s atmosphere.

In these poor seeing conditions, planets would twinkle like the stars do except that the planets are close enough and big enough to not be noticeable.

When the light of the star hits for example a pocket of either hot or cold air in the atmosphere, the light will be bent or refracted several times  in random directions.When the light bends like this the star appears to wink out briefly and our eyes interpret that as twinkling. Seeing conditions when stars are twinkling are not good and would be comparable to looking at stars near the horizon where the light has to go through more air and is susceptible to refraction.

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~ by sydneystargazers on October 26, 2009.

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