Celestia Forums

I'm trying to make a new pulsar addon, and I'm having some difficulties with the PrecessionRate command. What is the precession axis orientation ? How can I change its orientation ?

My impression is that it just rotates the body's rotational axis around an axis that's perpendicular to the ecliptic and that there's no way to change that reference orientation.
I could be wrong, though: it might be referenced to the plane of the body's own orbit.

Only Chris and Grant know for sure

All orbits in Celestia, including those of bodies outside the solar system, are referenced to the plane of the Solar System's ecliptic. You might try different orbital planes (different Inclinatin values) to see if the precession axis changes.

I tried changing the orbital parameters, but it doesn't seems to affect the precession axis. IMHO, Chris should add an option to control the precession axis orientation.

selden wrote:My impression is that it just rotates the body's rotational axis around an axis that's perpendicular to the ecliptic and that there's no way to change that reference orientation.
I could be wrong, though: it might be referenced to the plane of the body's own orbit.

Only Chris and Grant know for sure

Correct, precession always occurs about an axis perpendicular to the ecliptic. That's OK for the Earth, but there needs to be more flexibility.

All orbits in Celestia, including those of bodies outside the solar system, are referenced to the plane of the Solar System's ecliptic. You might try different orbital planes (different Inclinatin values) to see if the precession axis changes.

Actually, objects orbiting planets are referenced to the equatorial plane of the object they orbit. This is a shortcoming of Celestia that I will soon be correcting, as it's often convenient to specify an orbit referenced to the ecliptic plane.

--Chris

chris wrote:Correct, precession always occurs about an axis perpendicular to the ecliptic. That's OK for the Earth, but there needs to be more flexibility.

Chris,

we really need an option to select the precesion axis orientation. Something like this :

PrecesionAxis [x x x]

Where x x x = 0 0 0 is the default value (relative to wathever reference system). I would prefer the default orientation defined relative to the object's orbit, instead of Earth's ecliptic.

This option should be extremelly important for pulsars addons.