These ready-made modules are for the VSOP87 theory series C. They compute the ecliptical XYZ-coordinates for the planets Venus to Neptune referred to the mean ecliptic and equinox of the date (TT) for any given mo- ment over spans of thousands of years as given below. NOTE: The current value of the Astronomical Unit is 149597870.700 km, however, the value used in the VSOP87 theory is 149597870.691 km. The time argument is the JD (Julian Date) for a given date and time TT. BODY EPHEMERIS SPAN ======= ================== Sun 2000 BC to 6000 AD Mercury 2000 BC to 6000 AD Venus 2000 BC to 6000 AD Earth 2000 BC to 6000 AD Mars 2000 BC to 6000 AD Jupiter 1 AD to 4000 AD Saturn 1 AD to 4000 AD Uranus 4000 BC to 8000 AD Neptune 4000 BC to 8000 AD ============================== The computed XYZ-Coordinates are the actual heliocentric ecliptical coordin- ates at the given moment in AUs (Astronomical Units). Local corrections, such as for light-time, aberration, nutation, must be made to obtain the true local apparent coordinates from which the apparent geocen- tric coordinates may then be derived. These adjustments are applied later. The theoretical heliocentric precision of the VSOP87 theory is to within ± 1" |