I am working with the Keplerian Elements from the JPL web site. a - Semi-Major Axis e - Eccentricity I - Incilination L - Mean Longitude long.peri. - Longitude of the Periapsis long.node.or N - Longitude of the Ascending Node http://ssd.jpl.nasa.gov/txt/p_elem_t2.txt From this you can derive MA - Mean Anomaly EA - Eccentric Anomaly v - True Anomaly r - Radius Equ - Vernal Equinox All of this data revolves around the v=0 point or the Periapsis, the point where the elliptical orbit is the closest to the sun. Now from this point the Vernal Equinox can be derived. The Vernal Equinox occurs on about March 21 every year. When looking thru the Sun on 3-21 the constellation that you see is Pisces. At the angle (the Sun to Pisces from the Periapsis) is the basis of the reference angle for the start of the Ascending Node, I think. It comes out to be 270.02 for the Earth. The data seems to be coming out right, Equ+N+w+v=0 @ 12-21, Equ+N+w+v=90 @ 3-21, Equ+N+w+v=180 @ 6-21 and Equ+N+w+v=270 @ 9-21. I just want to know If I am way off or I am right on target.