Celestia Forums

The Windows package is available here:

http://www.shatters.net/celestia/files/celestia-win32-1.3.0pre5.exe

There are only a few small changes from prerelease 4:

- Flipped textures fixed on some asteroids
- All named moons in the solar system now included
- Added additional digits to time stored in cel:// URLs
- Fixed ARB_vertex_program path so it doesn't use NV_vertex_program functions

--Chris

a quick question, Do pluto and charon revolve around eachother in this? if not are there plans for it?

Darkbolt wrote:Do pluto and charon revolve around eachother in this? if not are there plans for it?

Charon revolves around the centre of Pluto in Celestia, instead of the more realistic revolution of both objects around their mutual centre of gravity, if that's what you mean. The relative positions and eclipse timings are unaffected by this. The only resulting error is with reference to the background stars, and it's of the order of a Pluto diameter - a tiny error as viewed from the Earth, especially since the available equations for Pluto's orbit aren't very accurate.
The difficulty is that Celestia doesn't currently support barycentres - every object must be in orbit around another object, not a point in space. But if you want to see Pluto and Charon in their correct mutual orbital relationship, download my transparent placeholder from Selden's website at http://www.lns.cornell.edu/~seb/celestia/hutchison/empty.3ds, and drop it into your Celestia models folder. Now paste the following code into solarsys.ssc. (In the first instance, it's interesting to add this code to the existing Pluto/Charon definitions, so that you can compare the position of the two bodies in the different versions.)
Grant

Thanks, I'll be sure to try that out :D

granthutchison wrote:But if you want to see Pluto and Charon in their correct mutual orbital relationship, download my transparent placeholder from Selden's website at http://www.lns.cornell.edu/~seb/celestia/hutchison/empty.3ds, and drop it into your Celestia models folder. Now paste the following code into solarsys.ssc.

I think the problem is exactly the same for all planets with moons. Maybe not the Earth-Moon system since both have custom orbits.
It is a long time I thought of your way to model the bayrenter orbits, but could you tell us, Grant, how accurate this is.

Calculus wrote:I think the problem is exactly the same for all planets with moons.

The difference is that all the others (apart from Earth-Moon) have mass ratios that put the barycentre of the system very close to the centre of the parent planet, so the Celestia solution is pretty much indistinguishable from the real motion. Earth-Moon is, as you say, dealt with very well by CustomOrbits. So Pluto is the only planet in the solar system for which the barycentre model makes a significant improvement to the appearance.

Calculus wrote:It is a long time I thought of your way to model the bayrenter orbits but could you tell us, Grant, how accurate this is.

Pretty good. The orientation of the current Pluto-centred solarsys.ssc orbit for Charon is taken from J2000.0 Horizons data. Pluto-Charon are pretty Keplerian in their behaviour - there's only a very slow drift of node and pericentre with time, so the orbital orientation should stay tight for years (and is unlikely to be significant in any case, given the low inclination and eccentricity).
All I did to quickly come up with barycentre-based orbits for Darkbolt was to split the semimajor axis between the two bodies, according to the known mass ratio of Pluto and Charon, and to ensure that the pericentre of Pluto was opposite the known pericentre of Charon. Charon therefore remains in the same orbit relative to Pluto, but Pluto now shifts a little from side to side.
I can probably tighten it a little more by obtaining barycentre orbits for both bodies from Horizons, but I think the major positioning error is going to arise from the theory for the orbit of Pluto, which isn't nearly as tight for the other planets.

Grant

granthutchison wrote:The difficulty is that Celestia doesn't currently support barycentres - every object must be in orbit around another object, not a point in space.

Lemme guess. This is also why binary stars aren't supported yet either?

Can we have barycenter support in a future release?

Chris a small request on models...

Would it at all be possible to revive haze and nightmaps for models? Also include bumpmaps and specular map assignments as scripts instead of programing it in the modeling software? Well in the upcoming 1.3.0. final if at all possible...

Also I remember you mentioned cloud bumpmapping at one point...Was that included already?

Once again thanks for your efforts...

One more thing chris...starnames...need I say more?

Well in depth there needs to be a way to change starnames in the stc or ssc files or the ability to create a new starnames.dat database in the data folder under the new addon structure...

I mentioned this in another topic a few days ago, but would it be possible to have more points on the orbit line for xyz files? It's annoying when this happens:


It's the same for all the spacecraft xyz's in celestia apart from one or two that only last a few years... It'd be great if this could be improved!

Thanks!

PS. The "minus 1 kelvin" thing is a bit odd too...