Star

Although it is commonly believed that the Lahiri ayanamsha places Spica at exactly 0 degrees Libra, most astrology software does not place Spica precisely at 0 Libra in the sidereal zodiac. There is a good reason for this: the proper motion of Spica would cause the sidereal zodiac to be oriented precisely to Spica rather than to most stars and to the galactic center. This is also true for the Fagan-Bradley ayanamsha which is based on placing the fixed star Aldebaran at exactly 15 degrees Taurus and for any sidereal zodiac based on the placement of a fixed star. Just as with the Lahiri ayanamsha, most astrology software does not place Aldebaran precisely at the specific zodiac position that it supposedly is placed at. If we were to use an ayanamsha that is based precisely on the position of a fixed star. then the wobble of the Earth would be considered completed when returning back to wherever the fixed star had traveled rather than in relationship to the fixed stars in general. With the help of diagrams and a table of positions of Spica and Aldebaran at 4 points in time, these concepts are described clearly so that you can understand appreciate why the precise position of a fixed star is not usually used as the basis of the sidereal zodiac.