In
astrology, your Rising Star Sign (sometimes referred to as
Rising Sign), is the
zodiac sign which corresponds to the sign on the eastern
horizon at the actual hour and minute of your
birth.
It is generally believed that your rising star is reflective of your sub-conscious personality. This is as opposed to your Star Sign, which is reflective of your conscious personality. This combination of factors goes a long way to explaining why there can be such vast differences in the traits of two people under the same sign.
People tend to get along well with others who's star sign is the same as their rising sign. For example, I am a scorpio, with cancer on the ascendant (my rising sign), and I get along very well with cancers, and all three water signs in general, (because I'm water/water). Liquidy.
Determining your rising sign requires a lot of calculations, I think. There are some books that have these pie-chart looking things, which make it real easy.