Observing double stars is a very attractive and interesting occupation. There is an enormous amount of double (and multiple) stars. Some of them are so close, that their binary signature can only be discovered by means of spectrography. Binary stars that are sufficiently apart so that they can be separated visually, are called 'visual double stars'. These stars are particularly interesting for amateurs. More, this is an area where amateurs can contribute scientifically with relative cheap and simple methods.
To observe double stars, you don't need a splendid and very dark sky. Light pollution is less disturbing and the transparancy of the sky is less important too. There is no problem observing double stars during full moon.
The most important properties of a double star are :
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•Separation : the (apparent) separation between both components ( in arc seconds)
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•Position Angle : the angle of the vector from the main star to the companion ( degrees ). This angle is measured from N (0 degrees), through E (90 degrees), S (180 degrees) and W (270 degrees).
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•The color of both stars.