Celestia Forums

Hi,

i am using Celestia 1.3.1 on a Windows 98 SE machine.

I tried to create a new star system at a distance of 30816 LY from Earth and encountered a problem.
After the creation of the *.stc and *.ssc files Celestia knows the star and planets and their positions, but when i execute GoTo, it will go where the star should be, but only shows the vastness of empty space!!! The same is true for some planets i created.

Yes i am a newbie, so i tried some examples from Seldens page, i.e. his HIP 500000 file.
This works really fine, so just took the file and played with it.
I set the distance from around 5500 LY to 3816 LY and it worked just fine.
But when i sat the distance to the desired distance of 30816 LY i had the same problem as before!

Does anybody know anything i did wrong??

Matlaf,

You did nothing "wrong", but you haven't read the "Preliminary User's FAQ" at the top of the User's Forum.

Celestia does not draw stars if they are more than about 16,000 Light Years away from the Sun.

I think I can remember a 16 kly distance limit for celestia.
This is due to a depth sorting capacity limit AFAIK. So you won't be able to put stars outside this limit.

maxim

Aye selden you caught me there. I didn't read the FAQ. going to change that right now.

Thanks 4 the answer anyway.

That 16k LY limit is a shame, cause i wanted to place my sunsystems at the "real" points in space where they are in the SciFi novel i read.

Well then i will just have to change my plans and put them closer to earth.

AFAIKs imposing a stellar distance limit. So what's going to happen when we want to begin recreating non-fictional systems in the LMC and SMC? And Andromeda?

Chris has mentioned that he has several ideas about how he might code around this problem, but they haven't come to fruition yet.

In the meantime, one workaround is to create a 3D model that consists of many individual points or objects, each one representing a star. That seems to work reasonably well, although it also has limitations: distant "stars" are the same brightness as nearby ones. Again, Chris has mentioned that he has some thoughts as to how this might be improved in a future version of Celestia.

For an example of how this might be done, see http://www.lns.cornell.edu/~seb/celestia/catalogs.html#3.5.6 and later sections. Those models happen to use points to represent galaxies and quasars, but the same methods could be used to draw stars.

Thanks selden, I hope there's a way to solve the brightness problem. Can't have HD5614 as bright as Venus.

--Starman

What about a 3D model that, instead of actually containing the stars themselves, was just a framework for the star locations, so that Celestia would load the model and place the appropriate star wherever there was a certain object in the 3D model.

Seems to me that Celestia could read the model and place the appropriate stars in their right locations.

Presumably the distance sorting problem means you can't have stars more than 16k lightyears from a given origin point, yes?

So why not have more than one origin? Say, at each point on a sphere of 16000ly radius around Sol at galactic coordinates of (0,0), (90,0), (180,0), (270,0), (0,+90), and (0,-90). Then you can refer to that origin somehow in the stc and say that the star is X ly from that point in Y direction.

It could all be done under the hood, so you input the co-ordinates of the star relative to Sol, and then Celestia figures out where that is relative to one of those alternative origins and plots it there.

This doesn't get rid of the distance problem, it would however mean that stars plotted relative to the alternate origins would be plotted when you entered their 'spheres of influence'. So you wouldn't see all the universe all at once, but you'd see the more distant stars once you got in range for them to show up in Celestia.

Would that work??