Astrologers use 12 of these constellations as signs of the Zodiac, omitting Ophiuchus, to make predictions. [Unlike astronomy, astrology is not a science.] Signs differ from constellations, bearing only a loose reference to one another. The sign of Pisces, for instance, corresponds to the rise of the constellation of Aquarius. Ironically, if you are born under a particular sign, that constellation it is named for is not visible at night. Instead, the sun is passing through it around that time of year, making it a daytime constellation that can't be seen.