Constellations

Constellations were officially designated in the 1930s. Boundaries were drawn along the celestial right ascensions and declinations. Today these boundaries have processed a small amount but the constellations still have their 1930's shape.

At one time, stars were frequently located in two or more constellations, simultaneously. Sometimes the star bore two names depending on which constellation you were considering. For example, Alpheratz (Alpha Andromedae) was a corner of the Great Square in Pegasus as well as the top of Andromeda's head. Today Alpheratz belongs entirely to Andromeda.

In addition to the 88 recognized constellations, there are many asterisms which are so known that people think of them as constellations. The Summer Triangle which inludes Lyra, Cygnus and Aquila, the Praesepe Beehive in Cancer, the Pleiades Seven Sisters and the Hyades, both in Taurus, are common examples.