The constellations are totally imaginary things that poets, farmers and astronomers have made up over the past 6,000 years. The real purpose for the constellations is to help us tell which stars are which, and as a guide for sailors to navigate at night. On a really dark night, you can see about 1000 to 1500 stars. Trying to tell which is which is hard. The constellations help by breaking up the sky into more managable bits. The International Astronomical Union divides the sky into 88 official constellations with exact boundaries, so that every direction or place in the sky belongs within one constellation. These are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages, and contains the signs of the zodiac.