I would like to look at the earth as if I'm standing on the sun,
meaning that I would like to see the slow annual drift of the earth axis
with respect to the sun's orbit.
I am sure it can be done, but just can't figure it out
Ren?©
looking at the earth from the sun
goto the center of the Sun (it's invisible from the inside)
track Earth
speed up time
It'll help if you include an Addon that draws a line through the Earth's axis.
One is available at http://www.lepp.cornell.edu/~seb/celest ... les.html#5
track Earth
speed up time
It'll help if you include an Addon that draws a line through the Earth's axis.
One is available at http://www.lepp.cornell.edu/~seb/celest ... les.html#5
Selden
selden wrote:Ren?©,
You have to determine what it is that's blocking your view.
Since I don't know where your viewpoint is located, I can't guess.
However, I don't know of anything that'd be likely, other than the Sun itself.
Yep; it seems to be the sun itself; how do I get to the middle of the sun,
and why should the sun be transparant when viewed from the middle ??
Ren?©
Hmmm. Going directly to the center of the Sun is a little more difficult than I thought.
One way is to create an invisible planet there. Here's an SSC catalog:
Hmm. It still doesn't work as well as I'd like.
3D objects in Celestia usually are invsible from the inside because of the design of their 3D models: their surface normals all point outward. Celestia draws a surface (makes it visible) only when its surface normals point toward the viewpoint. Unfortunately, since Celestia draws a photosphere around stars, that is still visible as a yellow glow. Also, I see flashing solar surfaces being drawn on my system. I suspect there's a bug in Celestia related to drawing a star from the inside.
It seems to work reasonably well when I define a dummy object that orbits just above the Sun's surface with the same orbital period as the Earth. Following that object and Tracking the Earth avoids the problems mentioned above. If you turn on the "Celestial Grid", you can see direction markers drawn around the Earth when you increase the magnification. They help to see how the Earth tips back and forth. They're drawn entirely behind the planet, though, so that the polar marks aren't drawn coming out of the Earth's poles.
One way is to create an invisible planet there. Here's an SSC catalog:
Code: Select all
"Center of Sun" "Sol" {
Class "invisible"
Radius 100
EllipticalOrbit {Period 1e32 SemiMajorAxis 0}
}
Hmm. It still doesn't work as well as I'd like.
3D objects in Celestia usually are invsible from the inside because of the design of their 3D models: their surface normals all point outward. Celestia draws a surface (makes it visible) only when its surface normals point toward the viewpoint. Unfortunately, since Celestia draws a photosphere around stars, that is still visible as a yellow glow. Also, I see flashing solar surfaces being drawn on my system. I suspect there's a bug in Celestia related to drawing a star from the inside.
It seems to work reasonably well when I define a dummy object that orbits just above the Sun's surface with the same orbital period as the Earth. Following that object and Tracking the Earth avoids the problems mentioned above. If you turn on the "Celestial Grid", you can see direction markers drawn around the Earth when you increase the magnification. They help to see how the Earth tips back and forth. They're drawn entirely behind the planet, though, so that the polar marks aren't drawn coming out of the Earth's poles.
Code: Select all
"Co-orbiting viewpoint" "Sun" {
Class "invisible"
Radius 100
EllipticalOrbit {
Period 1.0000
SemiMajorAxis 0.05
Eccentricity 0.0167
Inclination 0.0001
AscendingNode 348.739
LongOfPericenter 102.947
MeanLongitude 100.464
}
}
Selden
Unfortunately, not accurately.
As I understand it, it isn't handled properly when using the accurate VSOP-87 Earth and Moon orbits. However, if you're willing to use the less accurate Keplerian orbits (comment out the lines starting with CustomOrbit in data\solarsys.ssc), then you can add a PrecessionRate statement in the Earth's definition and it'll do something reasonable.
Unfortunately, I don't recall the units. I think it's degrees/day. (See the comment in solarsys.ssc about the PrecessionRate used for Hyperion.)
As I understand it, it isn't handled properly when using the accurate VSOP-87 Earth and Moon orbits. However, if you're willing to use the less accurate Keplerian orbits (comment out the lines starting with CustomOrbit in data\solarsys.ssc), then you can add a PrecessionRate statement in the Earth's definition and it'll do something reasonable.
Code: Select all
# CustomOrbit "vsop87-earth"
...
PrecessionRate nnnnn
Unfortunately, I don't recall the units. I think it's degrees/day. (See the comment in solarsys.ssc about the PrecessionRate used for Hyperion.)
Selden