Celestia Forums

Apparently the rotation axis of the moon is wrong in Celestia 1.2.4. It is shown parallel to earth's axis. In reality the moon's north pole should point approximately to the north pole of the ecliptic.

-Andreas

I suspected that this might be so-- the libration of the moon never looked quite right to me; it seemed that far too much of its far side became visible at times.

It seems that the inclination of the Moon's orbit to the ecliptic is really only about 1.5 degrees. (I can't, at the moment, find the longitude of the rotation axis. But I do know that some longitude figures in Celestia are interpreted as 90 degrees off, so I'm not sure I'd know what to do even if I had the right number.)

One thing I don't know is what the obliquity in Celestia's .ssc files is measured relative to: the ecliptic, or the planet's orbital plane, or the moon's orbital plane?

For that matter, I'm a bit confused about orbital inclinations of moons, too. It looks to me as if, for the moons of Saturn, the inclination is given relative to Saturn's rotational axis-- since I know that all of those inner moons orbit really close to the ring plane, which is equatorial, and Saturn's axial tilt is pronounced. Yet for Earth, the figure given for the Moon is definitely the one measured relative to the ecliptic, not the Earth's orbital axis. Is it wrong? I know that solar and lunar eclipses occur on the right dates, but the inclination relative to the ecliptic could be off without compromising that...