The spherical coordinates in this system are the heliocentric distance r, the ecliptic longitude λ, and the ecliptic latitude β, such that X = r \cos β \cos λ, Y = r \cos β \sin λ ...The spherical coordinates in this system are the heliocentric distance r, the ecliptic longitude λ, and the ecliptic latitude β, such that X = r \cos β \cos λ, Y = r \cos β \sin λ and Z = r \sin β. Heliocentric equatorial coordinates. \odot ξηζ with the \odot ξ axis directed towards the First Point of Aries and therefore coincident with the \odot X axis . The angle between the \odot Z axis and the \odot ζ axis is ε, the obliquity of the ecliptic.
