The 12 zodiac signs, measured more by the fixed stars and the constellations, not the seasons. The zodiac signs are still measured as 30 degrees of arc in length, and the "beginning point" is somewhat arbitrary (for example, not based on a particular fixed star). Pronounced: Sid-DEER-ee-al or Sye-DEER-ee-al.

Sidereal zodiac moves with the constellations. When the constellation of Aries moved, the constellation of Pisces moved into the position it vacated. Sidereal now calls the area of the chart traditionally ruled by Aries Pisces. The definition of the area is still the same, just the name was changed to show the movement of the constellations.

The measuring system in which a Planet is measured in relationship to a background of fixed stars. See Zodiac