The purpose of working with one's sidereal charts of conception and birth is to arrive at self knowledge and also to come to an experience of the living cosmos, which is possible through the sidereal frame of reference. Therefore all references to the zodiac in the following are in terms of the sidereal zodiac.1 It is called the sidereal zodiac because it is based on the stars (Latin for star: sidus, sideris) as they actually appear in the night sky. In the sidereal zodiac the twelve signs are defined in relation to the stars comprising the corresponding zodiacal constellations. The scientific definition of the zodiacal signs originated with the Babylonians who, in the world's first star catalog, specified the locations of the stars in each of the signs (Aldebaran at 15° Taurus, Antares at 15° Scorpio, etc.).
The signs are literally embedded in the zodiacal constellations. And the symbol (glyph) for any sign of the zodiac is based directly on the stars belonging to that zodiacal constellation. For example, let us consider how the zodiacal sign of Taurus is embedded in the constellation of the Bull. The midpoint of the sign, where the circle meets the crescent in the glyph, is marked by the star Aldebaran at 15° Taurus. This is the exact middle of the sign, since each sign is thirty degrees long. Thus, Aldebaran, marking the Bull's eye at 15˚ Taurus, is at the center of the sign and the constellation of Taurus.
Looking at the constellation of Taurus, it can be seen that the star cluster of the Pleiades is located on the upper part of the neck of the Bull. Correspondingly, the circle passing through Aldebaran and the Pleiades in the region of the neck of the Bull is represented by the circular part of the glyph. In the sidereal zodiac the Pleiades are located at 5° Taurus. Further, the two horns of the Bull are marked by the stars Elnath (28° Taurus) and Alhecka (30° Taurus), corresponding to the tips of the crescent surmounting the sign of Taurus - this crescent representing the horns of the Bull.
What is not generally realized is that all twelve signs of the zodiac - represented by their glyphs - originated directly from a perception of the flow of spiritual forces within the corresponding constellations.2 In this sense, the signs truly are embedded in the constellations of the zodiac. Looking up at the signs embedded in the constellations - in star-gazing fashion - enables one to enter into the flow of spiritual forces comprising a sign as represented by its glyph. In this way a direct experience of the being of a zodiacal sign is made possible. This experience is then intensified in the course of time through the continued practice of star-gazing. A "conversation" with the stars of a zodiacal constellation begins, thus attracting the essence of that sign - creating a resonance with the sign in the heavens. The creation of this resonance with a cosmic archetype is a matter of direct experience that grows in profundity in the course of time, so that repeated star-gazing enables one to come to ever deeper levels of comprehension of the spiritual nature of the zodiacal signs. Here it is a matter of entering into a "heart relationship" with the stars, in order for the heavenly conversation to take place.
Volumes have been written about the signs of the zodiac. Here it is a matter of considering the true origin of the zodiacal signs and how, through star-gazing, one can come into a living connection with the signs. Further material on the twelve signs of the zodiac is offered in the book Cosmic Dances of the Zodiac by Lacquanna Paul and Robert Powell.
1 The sidereal zodiac is the original zodiac of the Babylonians, Egyptians, Greeks, Romans, and Hindus. The sidereal zodiac was used by astronomers and astrologers for almost one thousand years before it became replaced by the tropical zodiac used in Arabic astrology, which was then introduced into Europe in the twelfth century AD. By and large it is the tropical zodiac that is used in modern astrology, with the exception of Hindu (Vedic) astrology that continues to use the sidereal zodiac. See Robert Powell's PhD thesis, History of the Zodiac (San Rafael: Sophia Academic Press, 2007).
2 Robert Powell, Hermetic Astrology, volume I, pages 230-237 depicts the zodiacal signs - the glyph being a portrayal thereof - embedded in the corresponding zodiacal constellations. See also Robert's works The Sidereal Zodiac (co-authored with Peter Treadgold) and The Zodiac: A Historical Survey.