Beltane -- Holiday Details and History
Beltane is the last of the three spring fertility festivals, the others being Imbolc and Ostara. Beltane is the second principal Celtic festival (the other being Samhain). Celebrated approximately halfway between Vernal (spring) equinox and the midsummer (Summer Solstice). Beltane traditionally marked the arrival if summer in ancient times.
At Beltane the Pleiades star cluster rises just before sunrise on the morning horizon, whereas winter (Samhain) begins when the Pleiades rises at sunset. The Pleiades is a cluster of seven closely placed stars, the seven sisters, in the constellation of Taurus, near his shoulder. When looking for the Pleiades with the naked eye, remember it looks like a tiny dipper-shaped pattern of six moderately bright stars (the seventh can be seen on very dark nights) in the constellation of Taurus. It stands very low in the east-northeast sky for just a few minutes before sunrise.
http://www.witchvox.com/va/dt_va.html?a=usma&c=holidays&id=2765