I just looked over your site...Nice work...I model a bit myself...
To answer your question, here is a sample taken from an ssc file...
"Name of Object" "Sun/Planet" << Or could simply be Planet...Replace with names of your choice...
{
Mesh "mymesh.3ds"
Texture "mytexture.jpg"
**[Note on texture mapping...Do the model WITHOUT a texture additive and map it using UWV in your Modifiers tab...I havent figured out how to remove a texture from an object so this could be a tricky task. But then applying the texture seems to work fine when saved as 3ds in the newer versions of Celestia...so it depends on the version your running]
Radius 83
EllipticalOrbit {
Period 95.829
SemiMajorAxis 94339
Eccentricity 0.2999
Inclination -01.18
MeanLongitude 754.568
}
RotationPeriod 12
Albedo 0.8
}
The additional values will affect its orbit, rotation and distance from the center of the planet it orbits...If its a planet its in kilometers...if its a star its in AUs...earth being 1 AU ~ 93 Million miles from the center of the sun...
Now for tilt and what not...Those values I will have to get back to you but I believe its the Obliquity value...
For rotation...I believe the model rotates on the Y axis...so face the top or bottom in that direction I do believe...
Material elements used in the model will consist of Opaque values only (This will make the object transparent like it does in MAX)...All others come out glossy no matter the Spectural or Glossiness values you set in MAX...So far I have found no others, but if you come across some...I would be interested in what those are
Theres maybe more but that should get you started...