Celestia Forums

I just downloaded celestia and am admitedly using it as a cheat to add in writing a novel.

What im trying to figure out is how to get the addons to actually show up in the program.

Admittedly I am a hardware tech by trade and training, so when it comes to anything outside an OS im lost.

Thanks for any help that can be provided

I cant see how celestia can help you in writing a novel. Care to enlighten us? As for the add-ons, Seldens intro should get you started:
http://www.lns.cornell.edu/~seb/celesti ... intro.html

Well, i dusted off an old sci fi short story that i wrote back in college, and decided to expand it out a bit. I just want to stay away from putting planets around stars that would either a) fry em, or b) freeze em. I remember enough from astronomy classes (my major was history, minor in anthropology) to know there is a very small threshold for life supporting planets.

Well, I got the info i needed, thanks for the info.

But problem two has popped up.

I got a little creative and built a mesh of babylon 4 and babylon 5. well, i tried to put them in orbit around eps eri b and failed. I couldnt even get the models to show up.

Everything worked fine till i put the voyager and pioneer addon's into the system, i dont think that should have created an issue, but hey, with a windows operating system everything is possible.

I even put the stations around single stars with no planets, the orbits showed but not the models

Im beginning to consider an uninstal and reinstall of the celistia software.

Otherwise this thing is great.

I always install and keep a second unmodified version of Celestia so I can compare what I've changed with what it came with. If you just reinstall without understanding what you've damaged, it's likely to happen again.

The symptoms you mention usually have nothing whatsoever to do with problems with Celestia itself.

In my personal experience, 3DS models usually don't show up because of typos --in their own names, in the names of their surface textures, or in the name of the directory where the texture files belong ([b[\textures\medres[/b]). The next most common problems are in the textures themselves: using images that are not a power of two on a side or that aren't of a type that Celestia understands (jpg, png or dds). The model is drawn, but without surface coloration, it's extremely hard to see. Make sure the surface normals point outward, too. Surfaces with their normals pointing away from the viewpoint aren't drawn.

Does this help?

Wonder if the model would show up IF the star it is orbit around is 6+ lightyears away????

no light that far out, if the software is modeled on ambient lighting.

Well, i tried putting the model in a place where the others show up, and bingo there it was.

Alright, now i got to figure out how to put the model at the L point between eps eri and its single planet. bbl

If you're close to them, Celestia draws all objects as if they were illuminated by the same light intensity. The rationale is that no display can come anywhere near to showing the correct intensity, and the eye would adapt to the ambient light level to show things at about the same brightness anyhow. If the surface texture image is dark, however, the object will be drawn proportionately dark.

There is a bug in v1.3.0 which causes objects more than about 20 or 30 au from the local star to be drawn dark. I don't know the exact distance involved. Combined with a dark surface texture, this also might explain your problem. This bug is fixed in the v1.3.1 prereleases, which are currently up to prerelease 9.

Note, however, that your descriptions of your problem are ambiguous. Is there something there which is just barely visible, or is there nothing there at all?

There is something there, you just cant see it at all, i put the same model in a different location (one that has no problems) and it shows up fine. the only thing i can figure is that considering that the orbit i set up, has the model some 6light years outside the system, and that wasnt my plan at all.

Im trying to recompute the orbit to get inside the orbit of eps eri b so that should, in theory solve the problem, and put the model at the approximate location it should in the first place.

Okay, i have taken the model and put it in place of the ISS, and three other stations i put around stars already.

The model shows up fine at those points, however, in the eps eri system, one i cant get the orbit where it should be, which is at the L1 point between eps eri and the b companion.

I am still trying to figure out the x y z coordinate system and how to set the orbit so it is stationary in relation to the planet.

If anyone can assist me on this project i would be more than happy, and if i can find a place to upload the models of babylon 4 and babylon 5 for people to get to, be more than happy to do that as well. With an ssc for the proper orbit if i ever figure it out.

If anyone has the x y z coordinates and orbit ssc for the L1 point between the earth and moon i would appreciate it. i am working on a habitate to place there based on some of the nasa ideas that were thrown around in the 60's and 70's

thanks

Adelvunegv_waya,

xyz trajectories really aren't useful outside the solar system.
They're created by asking JPL's Horizons ephemeris server to compute where an object will be and to return the heliocentric x, y, z and time values for a sequence of points along the object's path. Also, xyz trajectories are only good for a specific amount of time -- the period between the initial point and the final one.

So far as I know, nobody has written a program to generate this kind of track for objects in other stellar systems.

The easiest way to simulate an L1 orbit is simply to use exactly the same orbital parameters for the tertiary body (e.g. your habitat) as are declared for the secondary object (e.g. the moon). Then set the SemiMajorAxis value for the habitat to whatever is appropriate to put it at the L1 position -- at the distance from the center of the earth where the gravitational pulls of the moon and the earth are equal (i.e. 326054 km).

When copying the moon's orbital parameters, be sure not to include the "CustomOrbit" declaration. That overrides the EllipticalOrbit declarations, replacing them by Celestia's internal (much more accurate) formula for that specific body. Celestia only has formulas defining the orbits of some of the major bodies in the solar system. A CustomOrbit that specifies the name of any other body is ignored.

Does this help?

yes it does thanks

Addendum:

I hadn't actually looked at the Moon's orbital parameters in solarsys.ssc for a while. I hadn't realized that they're missing several values. (The actual orbital calculation is done by Celestia's internal 'CustomOrbit "moon" ', so them being missing doesn't affect where Celestia draws the Moon itself.) In particular, you'll need to add the AscendingNode and the ArgOfPericenter plus an Epoch and corresponding MeanAnomaly.

Some appropriate values can be found at
http://ssd.jpl.nasa.gov/sat_elem.html

Okay Seldon, this is what i have so far, now all i need is the epoch.


"Earthhab" "Sol/Earth"


{
Class "spacecraft"
Mesh "EarthL1.3ds"
Radius 1.0
ElipticalOrbit
{
Period 27.321661
SemiMajorAxis 326054
Eccentricity 0.054900
Inclination 5.16
AscendingNode 125.08
LongOfPericenter 135.27
MeanLongitude 16.17
}


Okay this is what i have and i still cant get it to show up in the software

"Earthhab" "Sol/Earth"
{
Class "spacecraft"
Mesh "EarthL1.3ds"
Radius 1.0
ElipticalOrbit
{
Epoch 242865.5
SemiMajorAxis 326054
Eccentricity 5.16
AscendingNode 125.08
LongOfPericenter 135.27
MeanLongitude 16.17
}

The second one is missing the period.
The Period and SemiMajorAxis are Celestia's minimal requirements for an EllipticalOrbit definition.

Oh, and you're misspelling EllipticalOrbit: it contains a pair of ells at the beginning.

Mesh "EarthL1.3ds"
Radius 1.0
EllipticalOrbit
{
Epoch 242865.5
Period 27.321661
SemiMajorAxis 326054
Eccentricity 5.16
AscendingNode 125.08
LongOfPericenter 135.27
MeanLongitude 16.17
}
RotationPeriod 1.0 # Essentially no rotation . . .
Orientation [ 90 0 0 0 ]
Alright, this is the ssc file, and still no sat in orbit... i know it has to be something simple i missed but im stumped

Well, this time you left off the part that tells Celestia the name of this object and what other object it's orbiting. I dunno if your cut and paste missed it or if it's not in the file.

In general, it's easiest to debug such things if you have each object defined in its own SSC file. That makes it easier to include everything because you can use a Ctrl-A or the menu item "edit/select all" to make sure everything is copied to the clipboard and thus included in the "paste".

I'll be looking in more detail, but I can't do it right now.

Here is the complete ssc file.

"Earthhab" "Sol/Earth"
{
Class "spacecraft"
Mesh "EarthL1.3ds"
Radius 1.0
EllipticalOrbit
{
Epoch 242865.5
Period 27.321661
SemiMajorAxis 326054
Eccentricity 5.16
AscendingNode 125.08
LongOfPericenter 135.27
MeanLongitude 16.17
}
RotationPeriod 1.0 # Essentially no rotation . . .
Orientation [ 90 0 0 0 ]


Seldon, i appreciate your help, but i cant help but think you are about to tell me to unload the software and go to basket weaving like the rest of my native american realitives.

I mean it has to be something simple. But i cant figure out what it is. Give me a hardware or OS problem and i can usually have it figured out in a few minutes.

That is what is really driving me nuts, i can make things work in a windows enviroment that usually dont (I am running an infobot on windows that is designed to run only in unix)

Umm....I think you're missing the last curly bracket on the end (What the heck are thay called..... umm...one of these "}")

BTW, Celestia data files have a bit of a learning curve to them....keep trying, and it'll all come naturally.

I built my first solar system in a week from the ground up, and a program to generate asteroid belt data files in two (But I had time and a very patient wife)

Best of Luck,

Cormoran

It looks like you managed to merge two of the orbital elements. I'm guessing a twitch of the wrist caused the end of one line and the beginning of the next to be deleted. Specifically, the value for the orbit's inclination is being used as its eccentricity, turning it from an almost perfect circle into a highly extended hyperbola.

It also turns out that defining a lunar L1 orbit is trickier than one might expect. Celestia expects a satellite's orbital parameters to be referenced to the equatorial plane. Instead, Lunar orbit parameters are referenced to the ecliptic. You can get around this somewhat by putting the habitat in orbit around a "dummy" planet that's hidden within the Earth. The result still isn't quite right though.

Someone like Grant Hutchison can probably come up with something better without even thinking about it

Still back to the original model problem, i get it to show up in every viewer but in celestia. if anyone wants to look at the model to see what they can determine, send an email to kwnitedemon2@yahoo.com ill be glad to send it to you

the texture files are in celestia textures/medres and when i built the model, i loaded textures straight out of that folder so all model references point straight there, unless the individual componants needs to be in the model folder itself?

i can try that next i suppose

As for the L1 orbit still havent got that to work yet either, but im not giving up