Where's the Globular Cluster Generator?

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TranslightDefender
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Where's the Globular Cluster Generator?

Post #1by TranslightDefender » 19.03.2011, 19:28

I've heard of the Globular Cluster Generator, and I found it here:
viewtopic.php?f=4&t=1320
but the links are broken.
Is there another place I can get it? Are there any other programs that can generate lots of stars to make clusters and galaxies in Celestia?
Am I correct in that the Globular Cluster Generator can add planets to the stars?
I know of StarGen which can generate planets for one star at a time.
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Re: Where's the Globular Cluster Generator?

Post #2by t00fri » 19.03.2011, 20:01

Celestia has a globular cluster generator built in. This way all 153 globulars of the Milkyway are displayed correctly. You can always add globulars of your gusto by adding corresponding entries in the globulars.dsc file. I have coded the generator according to scientific facts, but hopefully this will not disturb you too much... ;-)

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Re: Where's the Globular Cluster Generator?

Post #3by TranslightDefender » 19.03.2011, 20:06

Er... I can define galaxies in Celestia too.
I want to make lots of individual stars for galaxies and clusters.
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Re: Where's the Globular Cluster Generator?

Post #4by t00fri » 20.03.2011, 00:26

TranslightDefender wrote:Er... I can define galaxies in Celestia too.
I want to make lots of individual stars for galaxies and clusters.

Yes, But above you were asking for globulars. By default I allowed 8192 stars per globular. This number can be made e.g. 100000, but then you've got to recompile Celestia's source code. Also depending on your computer 100000 stars/globular will slow you down quite a lot....

Celestia 1.6.0 contains ALL known globulars of the MilkyWay.

Galaxies are more complex. You may easily add individual stars to galaxies.
Here is a thread of mine in our CelestialMatters site, that describes how to do this

http://forum.celestialmatters.org/viewt ... 10&start=0

I've also made a video.
http://www.celestialmatters.org/users/t ... milky3.avi
Here is another one with the MilkyWay viewed sideways. You can do this for any galaxy in Celestia.

In the videos, the observer does a virtual travel to the center of the MilkyWay...in Microsoft MP4 (AVI) format, which works well with the Windows MediaPlayer 11 and VLC, of course. Don't cut it off too early! It should be rather self-explanatory after my comments in the quoted thread. The stars are circling the MilkyWay's central Black Hole.

Since I am not for fictional stuff in Celestia you might better communicate with someone else.
There are plenty of SciFi fans etc in this forum.

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Re: Where's the Globular Cluster Generator?

Post #5by MiR » 20.03.2011, 01:43

TranslightDefender wrote:Imagination is more important than knowledge - Einstein
wise words - without "imagination" there's no knowledge. :!: :arrow: :idea: :wink:

I've installed two (better three) versions of Celestia. One is pure scientific; only verified data. The other one is with "impressions";
e.g.: Cham's BlackHoles or his MagneticFields, archaic-Earth addons, my 51Pegasi/b as well... and "high quality" SF (worth seeing!) from Reiko, Tim, Runar (of course) and some others...
Third version is - with minimal configuration - my working-zone-Celestia, just for testing the work and downloaded add-ons.

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Re: Where's the Globular Cluster Generator?

Post #6by TranslightDefender » 20.03.2011, 03:01

t00fri wrote:Yes, But above you were asking for globulars. By default I allowed 8192 stars per globular. This number can be made e.g. 100000, but then you've got to recompile Celestia's source code. Also depending on your computer 100000 stars/globular will slow you down quite a lot....
I'm confused. Celestia either has a star generator built-in or automatically generates stars for globulars? Am I completely misunderstanding you?

I said "globular" because that's what Rassilon named it, unless I'm mistaken.

I watched the video while doing some browsing throughout the forum today. Cool. 8)

MiR wrote:I've installed two (better three) versions of Celestia...
I have various versions, one plain, one with real addons, another with fictional addons, and one with my own fictional addons. :)
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Re: Where's the Globular Cluster Generator?

Post #7by t00fri » 20.03.2011, 11:45

TranslightDefender wrote:
t00fri wrote:Yes, But above you were asking for globulars. By default I allowed 8192 stars per globular. This number can be made e.g. 100000, but then you've got to recompile Celestia's source code. Also depending on your computer 100000 stars/globular will slow you down quite a lot....
I'm confused. Celestia either has a star generator built-in or automatically generates stars for globulars? Am I completely misunderstanding you?

Globular clusters are very dense (~spherical) clusters of many stars. The radial luminosity distribution of globulars follows closely the theoretical distribution by I.King that depends on measured parameters, like the central King concentration, the core radius, the 25mu isophote radius and the tidal radius. The star density of a globular is so high that with the naked eye, you will only be able to see a diffuse round blob whose light distribution is characteristic for a given globular. Here is an example for M55 (as resulting from my globular generator built into Celestia)

Image

Only when looked at with higher zoom (corresponding e.g. to a telescope) M55 will reveal an increasing number of individual stars. Here are again the images from Celestia

Image

Image

Hence, in order to generate by computer a globular cluster, one has to generate a large number of random stars that are distributed in space such that the known, measured light distribution is reproduced. Furthermore, the known brightness mix of globular stars and their color distribution have to be met by the random star generator.

All this requires good knowledge in probability techniques. Like e.g. the VonNeumann rejection-acceptance algorithm that allows to generate random data that are distributed according to an arbitrary prescribed probability distribution. Moreover, one has to carefully speed-tune such a generator in order not to slow down other important tasks in Celestia. All this I have implemented into Celestia years ago, together with the scientific data for each of the 153 known globular clusters in our galaxy.

Celestia does not have a built-in star generator for normal background stars. These are rendered according to the scientific data files from the Hipparcos catalog. Note that Celestia is first of all based on scientific standing, however, allows to add-in also plenty of fictional features by users.

I said "globular" because that's what Rassilon named it, unless I'm mistaken.
It seems you were lacking the meaning of the astronomical definition of a globular star cluster? If yes -> see my short summary in the previous paragraph.

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Re: Where's the Globular Cluster Generator?

Post #8by selden » 20.03.2011, 21:55

McLuster seems to be a reasonable stand-alone generator of clusters of stars.
http://www.astro.uni-bonn.de/~akuepper/ ... uster.html
Its output would need to be translated into Celestia's format, though. It's normally used to generate input for nbody6.

p.s.
starlab includes several cluster generators, each generating a specific density profile.
http://www.sns.ias.edu/~starlab/index.html

Both of these sets of tools are intended for use on Linux systems, although they compile and run under Cygwin on Windows computers.
Well, McLuster does; I dunno about starlab yet. It's taking a very long time to build.

p.p.s.
Building starlab failed after about 45 minutes but it seems to have built all the necessary utilities. They generate what looks like reasonable output, although it's extremely verbose.
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Re: Where's the Globular Cluster Generator?

Post #9by NoXion » 11.04.2011, 08:57

Apologies in advance if I am performing "thread necromancy", but this bothered me, so...

t00fri wrote:Celestia does not have a built-in star generator for normal background stars. These are rendered according to the scientific data files from the Hipparcos catalog. Note that Celestia is first of all based on scientific standing, however, allows to add-in also plenty of fictional features by users.

The globular clusters produced by default in Celestia are pretty indeed, and their accuracy is impressive. But what TranslightDefender wanted (I think) was a program by Rassilon(?) that generates globular clusters with actual stars that one could visit, some of them complete with planetary systems. In other words, the program generates globular clusters based on .STC (with an associated .SSC for the planets) rather than the ones based .DSC files which you seem to be talking about.
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Re: Where's the Globular Cluster Generator?

Post #10by TranslightDefender » 11.04.2011, 16:49

NoXion wrote:But what TranslightDefender wanted (I think) was a program by Rassilon(?) that generates globular clusters with actual stars that one could visit
Right.
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Re: Where's the Globular Cluster Generator?

Post #11by selden » 11.04.2011, 18:24

I've asked Chris if he can restore Rassilon's directory. It may take a while, assuming that it didn't get lost when the previous incarnation of Shatters gave up the ghost.
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The WayBack Archive site has it!

Post #12by selden » 26.05.2011, 17:04

The WayBack Archive site provides a backup of many public Web sites. Archive.org snapshots the entire readable Web about every six months.

Rassilon's directory, including the Cluster Generator, is available at
http://web.archive.org/web/200904212207 ... ~rassilon/
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