Pisces, one of the dimmest constellations of the zodiac, lays just north of the celestial equator. It is located east of the constellation Aquarius, south of Andromeda and Pegasus, west of Aries and north of Cetus. For stargazers in the Northern Hemisphere, Pisces is visible before midnight from August through February. Its highlights include a circlet of stars marking the western fish's head and the 10th magnitude spiral galaxy M74.
The sun travels through Pisces from March 13 to April 19. This span of time includes the first day of spring, also known as the vernal equinox. In astronomical terminology, the vernal and autumnal equinoxes are defined as the coordinates in the sky where the sun's path (the ecliptic) crosses the celestial equator.
Over 2,000 years ago, the vernal equinox was located farther east in the constellation Aries. This gave rise to the term "first point in Aries". The reason this point has shifted westward over the centuries is a phenomenon called the precession of the equinoxes. The earth's rotational axis wobbles like a top with respect to the distant stars. One cycle or wobble takes 26,000 years. Six centuries from now, the vernal equinox will shift westward into the constellation Aquarius. Adherents of astrology will be interested to know this will mark the official beginning of the age of Aquarius.