Hi,

I've got a problem: I have the routines to calculate the State vector of the bodies of our solar system from JPL, but the result vectors are referred to the equator and equinox of J2000 - meanwhile, is possible from this results calculate the orbital elements, but they will still be referred to the same point and plane. How can I convert this information to another epoch and relative to the ecliptic plane instead? I'm able to do the first part - the precession and nutation. But the simple rotation around the x-axis by the value of the obliquity doesn't give acurate results - maybe I'm doing something wrong. Plus the calculation of the passage trough the Perihelion is giving me results with no sense ( does anyone has the formulas for this?)

Please - someone - answer as soon as possible.

Best regards,

Kepler