|Object||x||y||z||distance in AU||Mag||Elong||Con|
I obtained orbital elements for the four major asteroids using the JPL Small-Body Database Browser:
1 Ceres, 2 Pallas, 3 Juno, 4 Vesta.
I also added "67P/C-G" in the table for comet 67P/Churyumov-Gerasimenko.
The sky coordinates calculated here will generally be within 2 or 3 arcminutes of accuracy (about one-tenth the apparent angular diameter of the moon), although results will be worse for the asteroids (Ceres, Pallas, Vesta, and Juno) for years before 2010 or after 2020. This is because I calculate asteroid orbits as perfect ellipses that closely approximate their behavior in 2015, but I do not correct for how these orbits drift over time. I intend to update this page every year or two to use the latest orbital elements for these asteroids, so that calculations for nearby dates will always be reasonably accurate. If you need really accurate data for a planet or asteroid, try the JPL HORIZONS System. (These guys were navigating spacecraft through the solar system when I was still playing with GI Joe!)
Other useful astronomy calculation resources: