I am building a 3d solar system simulation using WebGL and have come across the problem of establishing the direction of tilt of the various planets. No I know the tilt of the planets in degrees what I don't know is the direction of the tilt.
Consider the following, on earth summer solstice (on the northern hemisphere) is on the 21st of June. So on that day the north pole is tilted towards to sun. Good times from this I can figure out which way in the 3d coordinate system to actually tilt the earth those 23.5 degrees.
However how and or where do I find out the same information for all the rest of the planets. There is a wikipedia article (for instance) on seasons on Mars that has the dates for the equinoxes for Mars.
Any idea where I could find similar information for all the planets, or better yet, an ever better way of determining the direction of the tilt of the planets.