Celestia Forums

And it is inclined with respect to the equator -something I would have thought was impossible. If I recall correctly that would be quite difficult to do in Celestia.

eburacum45 wrote:And it is inclined with respect to the equator -something I would have thought was impossible. If I recall correctly that would be quite difficult to do in Celestia.

As Celestia's premise seems to be to show things as they would appear to the naked eye, then I guess it's not really an issue for this, as it's only visible in Infra-red wavelengths.

Tonight I tried to figured out this great ring. As start I wrote this code:



in which the mesh is a single vertex point with a virtual Saturn's radius (it rest always a point, unclickable and invisible inside Saturn, but that radius allows the Rings directive).
As you can see there aren't inclinations of some sort. Now, in the forementioned articles is said that the great ring is "on a different plane", "inclined of 27 degrees".
Could someone tell me why with the above SSC I get the great ring just inclined of 27 degrees (red orbit is the great ring)? The mesh point is not oriented, though. Whether I orient it as usual [ 90 1 0 0] the ring is at 90 - Saturn inclination.


Note: one can try, just replace "Mesh" and "Texture"

EDIT LATER:

Ok, even though this is not 27 degree but the 28.052 of UniformRotation > Inclination, how I orient this great ring?

Rings are drawn in the equatorial plane of their parent object.

You have to define a fake Saturn which has the correct Inclination defined in its UniformRotation statement.

You have defined your fake Saturn to have an inclination of 0 degrees relative to the Ecliptic plane. The real Saturn has an inclination of 28.052 degrees relative to the Ecliptic plane, so your rings have an inclination of 28.052 degrees relative to Saturn.

selden wrote:Rings are drawn in the equatorial plane of their parent object.

You have to define a fake Saturn which has the correct Inclination defined in its UniformRotation statement.

You have defined your fake Saturn to have an inclination of 0 degrees relative to the Ecliptic plane. The real Saturn has an inclination of 28.052 degrees relative to the Ecliptic plane, so your rings have an inclination of 28.052 degrees relative to Saturn.

But this inclination is an interaction between CustomOrbit "vsop87-saturn" and BodyFrame { EclipticJ2000 {} } ? Because my "EDIT LATER" is achieved by reasoning, nor because I've put the UniformRotation statement in my SSC. So just need to add:
UniformRotation
{
Period #10.65622222 # System III (magnetic field)
Inclination -1.052 # 27 - 28.052
AscendingNode 169.528
MeridianAngle 358.93 # correct System III prime meridian
}
where Period, AscendingNode and MeriadianAngle are guess? Anyhow, thanks Selden for reply.

The OrbitFrame statement tells Celestia what coordinate system to use when determining the object's location in space. The default OrbitFrame is "Ecliptic J2000" for planets and "Equatorial J2000" of the parent body for moons.

The BodyFrame statement tells Celestia what coordinate system to use when determining the object's orientation in space. The default BodyFrame also is "Ecliptic J2000" for planets and "Equatorial J2000" of the parent body for moons.

There is no interaction between OrbitFrame and BodyFrame.

If the defaults are OK, then you don't have to specify either OrbitFrame or BodyFrame, but I find it easiest to understand what is happening by specifying OrbitFrame {...} followed by a position statement like FixedPosition or EllipticalOrbit, then BodyFrame {...} followed by an orientation statement like FixedRotation or SampledOrientation.

For example this code:

"Great Saturn Ring" "Sol"
{
Class "diffuse"
Clickable false

Mesh "great_saturn_ring.cmod"
Radius 60268

OrbitFrame { BodyFixed { Center "Sol/Saturn" } }
BodyFrame { BodyFixed { Center "Sol/Saturn" } }

CustomOrbit "vsop87-saturn"

Rings
{
Inner 6000000 # includes some ringlets inside edge of C ring at 74660
Outer 13000000
Texture "great_saturn_ring.png"
}

Albedo 0.1
}

doesn't work. The rings doesn't appears. And they doesn't appears also when CustomOrbit is removed. Is a rings related problem?

It works for me when I eliminate the OrbitFrame.
The OrbitFrame above causes the fake planet to orbit around Saturn.
It needs to orbit around the Sun.

Ah! indeed, thanks.
Now, set apart the the Celestia's issues, this ring seem very distant from both Phoebe and Iapetus...

Fenerit wrote:Ah! indeed, thanks.
Now, set apart the the Celestia's issues, this ring seem very distant from both Phoebe and Iapetus...

The orbit of Phoebe is within the ring. Remember that this "ring" is not flat. It's more like a torus.

See the diagram at http://www.nasa.gov/mission_pages/spitz ... 1007b.html

It shows the orbit of Iapetus to be much closer to Saturn.

A candidate for Cham's particle modelling technique perhaps?

^^

ajtribick wrote:A candidate for Cham's particle modelling technique perhaps?

This would be easy, the problem is that without the point sprites, points only became more visibles with distance. There would be another SSC directive like: InvisibleAt <value in Km>...

I would suggest to associate a model to Saturn itself ("Small particles ring" "Sol/Saturn"), defined as Class "diffuse", with emissivity turned ON and clickable set to false. Also, this ring should be made invisible by default, and a celx script should be used as a visibility "switch".

I may built a new CMOD model for this ring, but I'm not sure it's really worth it yet.

Someone knows the true shape of this ring ? I need the internal radius (in km), external radius and thickness (in km).

I think at least some of the dimensions were given in one of the links in my first post of the thread, (but probably not enough to allow modeling). ... I suggest you wait awhile until full details are published.

Do you realize that this ring is completely invisible to the naked eye?

Forementioned articles given 20 times the Saturn diameter as thickness of the torus. 13 x 10^6 the outer radius and as inner radius TV broadcast have said 6 x 10^6 (this latter source do take with springs).

CC, what about of a Celestia's version with the views in ALL wavelenghts?

A detailed description of the large ring is in The Planetary Society's Blog at http://www.planetary.org/blog/article/00002165/

A couple of observations from reading that article...

1. The article quotes Saturn's radius as being 60,330 kilometers. In Celestia, it's 60,268 km.

2. The Moon S/2008 S1 (now named Aegaeon) and the associated G ring is not included in Celestia.

CC

A Web search has turned up several different values for the size of Saturn, but no mention of who did any of the measurements.

The orbit of Aegaeon is not well known. It's included in a supplemental Addon.
http://www.lepp.cornell.edu/~seb/celest ... moons.html