stars.txt

[ElChristou]

Vince, you are a King!

[t00fri]

Yes, Vincent,

with your little patch, now the barycenter is always marked. Very nice! In order that the barycenter can be click-selected thereafter, one has to take care of course that the limiting magnitude is sufficiently turned up (]-key)!


Cheers,
Fridger

[Vincent]

Vince, you are a King!

No Pleeeeeaaaaase... !

In order that the barycenter can be click-selected thereafter, one has to take care of course that the limiting magnitude is sufficiently turned up (]-key)!

Yes, of course.
Then, it would be great to make a marked object selectable by a click whatever its distance from the observer...

[ElChristou]

Your right, but don't worry, meanwhile you do some good job, this won't happen...

[hank]

Then, having the possibility to distinguish spectroscopic binaries from visual binaries in celx would be great. But since neither the name nor other properties show the difference between spect and visual binaries, the only way to do that would be to add the possibility to celx to track the filename from which the stars were loaded in the database.

Hank, do you think such a feature could be easily added to celx scripting ?

Not easily. As far as I recall, Celestia doesn't retain information about the files from which objects are loaded. In a future version of Celestia it might be possible to add an object attribute for the name of the definition file, or to allow arbitrary Lua-accessible object attributes to be specified in definition files.

Of course, you could use the Lua IO library to read the binary star definition files and extract the star names from them.

- Hank

[Cham]

The code modification appears to work nicely. Clicking on a binary selects the barycenter, if at some distance. Thanks Vincent.

[Vincent]

Of course, you could use the Lua IO library to read the binary star definition files and extract the star names from them.

Of course...

Thanks Hank.

[chris]

Chris once told that he wanted to change the ring code, to add some reflectivity (?) and other realistic effects to the rings.

There's quite a lot of work to be done to make the rings more realistic, especially as seen from the dark side. A recent post Planetary Society blog post by Emily Lakdawalla shows two images of Saturn that show just how profoundly different the sun-facing and shadowed sides of the rings appear:

http://www.planetary.org/blog/article/00001197/

In order to depict the rings accurately, we need more than an density and albedo map: we need a map that shows how the light scattering function varies through the rings. The Cassini division appears dark from the sun-facing side of the rings not because it's empty, but because the particles there are predominantly forward scattering (evident when you see the Cassini division glowing when the camera is on the shadowed side of the rings.)

This is definitely a topic for another thread, however.

--Chris

[chris]

After these extensive tests, the latest and apparently perfect CVS candidate versions of my visualbin.stc, spectbin.stc data files and the corresponding PERL scripts visualbin.pl and spectbin.pl are here

http://www.celestiaproject.net/forum/viewtopic ... &start=171

--------------------------------------------
They incorporate Cham's successful proposal to add 'AB' to the barycenter name, "HIP xxxxx AB", of binaries with only a HIP number designation (i.e no proper name). Only this way the present code allows to GOTO and select the respective barycenters.
Such binaries now are characterized by the triplet:

HIP xxxxx AB (barycenter)
HIP xxxxx A (A component)
HIP xxxxx B (B component)

-------------------------------------------

If Chris L. agrees, I'll commit them to CVS.

Of course, another (better) possibility is to modify the code to make the 'AB' addition superfluous.

There's another possible solution: we can actually make the object with catalog number xxxx the barycenter instead of the A component. In the .stc file, we currently have records like this:

Code: Select all

Barycenter "HIPxxxx"
{
}

xxxx "HIPxxxx A"
{
}

"HIPxxxx B"
{
}


It may make more sense to assign the HIPPARCOS catalog number to the barycenter instead of to a component of the system, like this:

Code: Select all

Barycenter xxxx "HIPxxxx"
{
}

"HIPxxxx A"
{
}

"HIPxxxx B"
{
}


Now, when you enter-select 'HIP xxxx', the barycenter is picked. That seems like correct behavior to me.

I'm a little concerned about the AB designation for barycenters because it could conflict with the convention we're using for star systems with more than two components. In a trinary system, with a two pairs of stars orbiting each other, the components are:

name Aa
name Ab
name Ba
name Bb

Thus 'name Ab' is a component designation that's identical to a barycenter designation apart from the case. Grant has used 'name A-B' to indicate barycenters in complex multiple systems in nearstars.stc--it's not required for binary systems if we adopt my proposal, but we could still add it as an alias for consistency.

--Chris

[t00fri]

There's another possible solution: we can actually make the object with catalog number xxxx the barycenter instead of the A component.
It may make more sense to assign the HIPPARCOS catalog number to the barycenter instead of to a component of the system, like this:

Code: Select all

Barycenter xxxx "HIPxxxx"
{
}

"HIPxxxx A"
{
}

"HIPxxxx B"
{
}


Now, when you enter-select 'HIP xxxx', the barycenter is picked. That seems like correct behavior to me.


--Chris

Yes that solution works fine and is preferrable.

I shall upload the binary orbit database right away with the modified syntax for further testing.

Bye Fridger

[t00fri]

Hi all,

please have a look at my next iteration of visualbins.stc & spectbins.stc, incorporating Chris L.'s proposal.

Here are again the download URL's:

the modified PERL scripts

http://www.celestiaproject.net/~t00fri/images/ ... ins.pl.zip
http://www.celestiaproject.net/~t00fri/images/spectbins.pl.zip

and generated .stc files for download and testing:

http://www.celestiaproject.net/~t00fri/images/visualbins.stc
http://www.celestiaproject.net/~t00fri/images/spectbins.stc

Bye Fridger

[ElChristou]

In many cases the orbits are not drawn, or some are missing in the systems... Why? no idea...

[Cham]

In many cases the orbits are not drawn, or some are missing in the systems... Why? no idea...

Can you give some specific examples ? I don't see any problem with this method yet.

[t00fri]

In many cases the orbits are not drawn, or some are missing in the systems... Why? no idea...

examples, please (HIP numbers!)
I can see NO problems!

Bye Fridger

[ElChristou]

Oops, sorry...

Go to EPS Ind, EPS Ind A (HIP 108870) has no orbit (perhaps because EPS Ind B is a barycenter?)

[t00fri]

Oops, sorry...

Go to EPS Ind, EPS Ind A (HIP 108870) has no orbit (perhaps because EPS Ind B is a barycenter?)

That's true. This is from Grant's nearstars.stc file, which does not concern me at least... It's kind of a pathological case...

You said many binaries don't show orbits. Which other ones?

Bye Fridger

[Cham]

Go to EPS Ind, EPS Ind A (HIP 108870) has no orbit (perhaps because EPS Ind B is a barycenter?)

True. EPS Ind A has no orbit, whatever the solution used : mine or Chris's.

Actually, there are two tiny dwarfs orbiting EPS Ind B : Ba and Bb. This small sub-binary is orbiting EPS Ind, with EPS Ind A as partner.

The "moral" of the story here is that barycenters don't show any orbits, in Celestia. This is actually the same case as for the Pluto-Charon system : their common barycenter orbit is invisible around our Sun (which is a bad thing, IMO).

[t00fri]

Orbits must anyhow be thoroughly revised! We have discussed that a long time ago.

The problem is the assumed frame independence of the orbit contours.

If one body is transformed into its rest frame, (which includes barycenters!), then the other bodies that encircle it have to move on drawn orbits around the first body at rest. In that frame all orbits MUST be stationary! (which they are not right now)

Bye Fridger

[Cham]

If one body is transformed into its rest frame, (which includes barycenters!), then the other bodies that encircle it have to move on drawn orbits around the first body at rest. In that frame all orbits MUST be stationary! (which they are not right now)

I totally agree with this.

[ElChristou]

...You said many binaries don't show orbits. Which other ones?

Cannot tell you right now because...

http://shatters.net/forum/viewtopic.php?p=94307#94307