Any interest in a command-line cluster generator?

[selden]

Is anyone interested in me providing a command-line driven cluster generator?

The initial version would have some severe restrictions. Primarily, binaries would work only under Cygwin for Windows ( See http://www.cygwin.com/ ). It might be possible to get the binaries to work without a full Cygwin installation, but I'm not sure.

I think it would be possible for someone (not me) to compile the source code for use under either MacOS or Linux.

Unlike Rassilon's cluster generator, this generator creates clusters consisting only of stars. No planetary systems are included.

Background:

I downloaded MCluster from http://www.astro.uni-bonn.de/~akuepper/ ... uster.html and built it under Cygwin for Windows. MCluster is a program which generates clusters for gravitational dynamics studies, providing input to NSTARS4 and NSTARS6. It is written in a combination of C and Fortran.

I then wrote a Fortran program to translate its output into STC format. It works fine for my purposes, but would need some cleaning up before I'd be willing to publish it.

Below are Celestia screengrabs of some of the types of clusters it can generate.
The pictures are all taken from the same viewpoint. All of the clusters shown consist of about 10,000 stars and have a half-mass radius of 5 parsecs. Three are distributions of stars corresponding to clusters with King W0 parameters of 0.5, 5 and 9.5. The other is a Plummer distribution. These are only a few of the options selectable in MCluster.

Another example of a Plummer disteribution with a much smaller radius and some problems is discussed in the thread "I can has stars?" at viewtopic.php?f=6&t=16487

[Hungry4info]

Well, upon trying to vote several times, I kept getting this over and over

The submitted form was invalid. Try submitting again.

I would be willing to give it a try.

[t00fri]

Selden,

while MCluster allows to set more parameters and cluster profiles, the cluster generator that I have implemented into Celestia produces virtually identical results for King profiles (only much faster) . The King profiles are usually preferred in astrophysical research work. Moreover, I have implemented the statistically known ratio of Red Giant stars. (In Celestia.Sci also a proper distribution of Blue Straggler stars was implemented.) . The default number of cluster stars in Celestia is 8192. Due to the speed-optimized algorithm that I have designed, one may easily use e.g. 100000 stars per globular! In Celestia, users may even fly right through the globular's core with a visual experience that is not entirely unrealistic...

So I really cannot understand what has led you to your above efforts.

In Celestia's globulars.dsc data file, the KingConcentration c, the CoreRadius r_c and the (mu25 isophote ) Radius R represent a complete set of parameters for specifying ANY King cluster shape! By choosing c and r_c appropriately, your above cluster images may be immediately reproduced.

People may easily add fictional globulars with desired shapes and concentration to Celestia's data file. This includes globulars in other galaxies.

Fridger

PS: In your above poll, I missed an important option:
"no command line cluster generator, although globulars are very interesting"

[selden]

Well, upon trying to vote several times, I kept getting this over and over

The submitted form was invalid. Try submitting again.

Which forum style are you using to view the Celestia forum?

A search of the phpbb site reveals that this is a bug which might be related to which style is in use, but they don't seem to have a fix yet.

I would be willing to give it a try.

Thanks! Do you already have Cygwin installed?

[selden]

Fridger,

While the globular cluster generator built into Celestia generates excellent "eye candy", it doesn't generate Stars. As a result, one cannot use them to do any of the things that one can do with Celestia's Stars. One cannot select an individual "star" in one of those clusters and travel to it, for example, or change their appearance with Celestia's "star style" command. Other things one cannot do include placing planetary systems around some of the "stars" and making them orbit around one another or around a common BaryCenter.

p.s. I added "I prefer a different cluster generator."
Unfortunately, it deleted all of the previous votes, Fortunately, there wen't many:
1 "I want"
2 "I'd like to try it"
1 "I want a GUI"

[t00fri]

Fridger,

While the globular cluster generator built into Celestia generates excellent "eye candy", it doesn't generate Stars. As a result, one cannot use them to do any of the things that one can do with Celestia's Stars. One cannot select an individual "star" in one of those clusters and travel to it, for example, or change their appearance with Celestia's "star style" command. Other things one cannot do include placing planetary systems around some of the "stars" and making them orbit around one another or around a common Ba\yCenter.

Yes, there are always things one cannot do. But MCluster itself can't do these things either. Only by printing the stars out individually and reading them into Celestia via a slow ascii data list, they are interpreted by Celestia as regular stars. I suppose that's what your FORTRAN program is good for.

But then you will be seriously limited by the number of cluster stars unlike Celestia's built-in generator: I can work easily with realistic numbers of globular stars like > 500 000. So there are always things one cannot do

It doesn't seem to make a lot of sense to me to land on a globular star (it's kind of hot there... ). Moreover, binary systems in globulars can at best be of interest for fictional applications, since no complete orbital parameter sets have been extracted by astronomers up to now. My limitation to King luminosity profiles had the simple reason that scientific parameter sets (c, r_c, R) for all MilkyWay globulars have only been catalogued for these most popular profiles!

Let me just add for completeness that my extended globular cluster code in Celestia.Sci actually generates the cluster stars into Celestia's star rendering buffer list, such that all usual star features (including Chris' new star patch) work correctly for each globular cluster. In addition, realistic color profiles are inferred by exploiting now the B-V color data from the globular cluster catalogs. Finally, the globulars of Celestia.Sci render all known "singing" pulsars in their cores. See also my CM "white paper" http://forum.celestialmatters.org/viewtopic.php?t=381

I didn't mention these features above since Celestia.Sci is not generally available yet.

Fridger

[ajtribick]

Regarding the need to put planets around cluster stars, if I remember correctly there is only one planet known in a globular cluster. Unfortunately the distances of PSR B1620-26 and M4 in Celestia are somewhat inconsistent...

[t00fri]

Regarding the need to put planets around cluster stars, if I remember correctly there is only one planet known in a globular cluster. Unfortunately the distances of PSR B1620-26 and M4 in Celestia are somewhat inconsistent...

Andrew,

I suppose the people who have an interest in Selden's cluster generator "suite" don't care much about the existence of scientific data for binary or planetary orbits in globular clusters.

Fridger

[Fenerit]

Let me just add for completeness that my extended globular cluster code in Celestia.Sci actually generates the cluster stars into Celestia's star rendering buffer list, such that all usual star features (including Chris' new star patch) work correctly for each globular cluster. In addition, realistic color profiles are inferred by exploiting now the B-V color data from the globular cluster catalogs. Finally, the globulars of Celestia.Sci render all known "singing" pulsars in their cores. See also my CM "white paper" http://forum.celestialmatters.org/viewtopic.php?t=381

I didn't mention these features above since Celestia.Sci is not generally available yet.

Fridger

You are saying that the new globular clusters will be no longer based upon sprites? And the King luminosity (concentration) could be set for the users like the usual stars does for magnitudes, that is, by pressing some keys until achieved its relevant maximum?

[t00fri]

Let me just add for completeness that my extended globular cluster code in Celestia.Sci actually generates the cluster stars into Celestia's star rendering buffer list, such that all usual star features (including Chris' new star patch) work correctly for each globular cluster. In addition, realistic color profiles are inferred by exploiting now the B-V color data from the globular cluster catalogs. Finally, the globulars of Celestia.Sci render all known "singing" pulsars in their cores. See also my CM "white paper" http://forum.celestialmatters.org/viewtopic.php?t=381

I didn't mention these features above since Celestia.Sci is not generally available yet.

Fridger

You are saying that the new globular clusters will be no longer based upon sprites? And the King luminosity (concentration) could be set for the users like the usual stars does for magnitudes, that is, by pressing some keys until achieved its relevant maximum?

Massimo,

I said that the cluster stars in Celestia.Sci are added to the render list for normal stars. How these are rendered then depends on the star style chosen.

As to the King profile parameters, one can just add fictional clusters to the globulars.dsc list and set the KingConcentration c, the CoreRadius r_c and the 25mu Isophote radius R to ones gusto.
People might also experiment with the effects of the concentration c on the cluster appearance by varying c between 0.3 and 2.5, say.

Fridger

EDIT: as to the cluster luminosity, it can indeed be attached to some key, which is trivial to code. I did it in one version but I am not sure yet whether I like it.

[Hungry4info]

Which forum style are you using to view the Celestia forum?

I'm using the 'Serenity DarkBlue' board style.

Do you already have Cygwin installed?

I don't.

[Fenerit]

It is a great enhancement, indeed. Even for fictional purposes of sky background's colorizing.

EDIT LATER:
Cross post with Hungry, of course.

[Fenerit]

EDIT: as to the cluster luminosity, it can indeed be attached to some key, which is trivial to code. I did it in one version but I am not sure yet whether I like it.

Good for you, which is "trivial to code"...

[selden]

Which forum style are you using to view the Celestia forum?

I'm using the 'Serenity DarkBlue' board style.

You might give subSilver a try the next time you get these kinds of errors.

Do you already have Cygwin installed?

I don't.

Unfortunately, I think the initial release of the generator will need Cygwin's runtime dll and its bash shell. That'd be just the minimum Cygwin installation, though, with no optional packages selected. While the generator might work with just Cygwin's dll installed by itself, I can't guarantee that.

[t00fri]

It is a great enhancement,

Since I am not sure what you are referring to , let me add that fictional globulars of arbitrary King-type shapes (c, r_c) can already be added in Celestia 1.6.0. Only the cluster stars are not real "Celestia stars" yet. That requires Celestia.Sci.

Fridger

[t00fri]

EDIT: as to the cluster luminosity, it can indeed be attached to some key, which is trivial to code. I did it in one version but I am not sure yet whether I like it.

Good for you, which is "trivial to code"...

Well sorry, it is certainly trivial for any Celestia developer. A less trivial issue is, however, that we don't have any free keys left!

Fridger

[Fenerit]

It is a great enhancement,

Since I am not sure what you are referring to , let me add that fictional globulars of arbitrary King-type shapes (c, r_c) can already be added in Celestia 1.6.0. Only the cluster stars are not real "Celestia stars" yet. That requires Celestia.Sci.

Fridger

I'm referring to the clusters like real "Celestia stars". I can't wait for Celestia.Sci, although I think such enhancement should be appreciated also within the next official versions.

[selden]

Only by printing the stars out individually and reading them into Celestia via a slow ascii data list, they are interpreted by Celestia as regular stars. I suppose that's what your FORTRAN program is good for.

Exactly. A few tens of thousands of stars in clusters seem to work fine in Celestia when running on modern computers and graphics cards. I have not yet tried larger clusters, nor have I tried to merge them with the binary star database file. Although that shouldn't be very difficult, I think it's important to be able to install clusters as Addons without disturbing Celestia's base distribution files. (i.e. it'd be nice if Celestia supported multiple binary star database files.)

binary systems in globulars can at best be of interest for fictional applications, since no complete orbital parameter sets have been extracted by astronomers up to now

One of the major uses of cluster generators like MCluster is in the study of how clusters evolve due to gravitational and other effects. The number of initial binary systems is one of MCluster's options. Translating MCluster's orbital state vectors into Celestia's Keplerian format is something I'd like to do eventually. I have not yet investigated the output format used by the NSTARS family of gravity simulators. That's another obvious project for the future, especially since NSTARS now supports the use of GPUs as computational accelerators.

I suppose the people who have an interest in Selden's cluster generator "suite" don't care much about the existence of scientific data for binary or planetary orbits in globular clusters.

I'll admit that my initial interest is to support artistic uses of Celestia. e.g. generating skies for planetary backgrounds in SF images or stories.

My attempts to generate more realistic clusters have been frustrated by the lack of data. Most cluster star catalogs have been generated from measurements made using CCD images or photographs of clusters' centers. The resulting rectangular clusters aren't particularly realistic or photogenic.

[t00fri]

binary systems in globulars can at best be of interest for fictional applications, since no complete orbital parameter sets have been extracted by astronomers up to now

One of the major uses of cluster generators like MCluster is in the study of how clusters evolve due to gravitational and other effects.

I doubt that much significant information about globular cluster evolution may be obtained without immerging a given cluster model into the gravitational force fields from the parent galaxy! This is standard knowledge. I have heaps of papers about this point.

Certainly there is a lot of simulation progress e.g. with NSTARS using CUDA or similar.

My attempts to generate more realistic clusters have been frustrated by the lack of data. Most cluster star catalogs have been generated from measurements made using CCD images or photographs of clusters' centers. The resulting rectangular clusters aren't particularly realistic or photogenic.

I am puzzled. What kind of data do you mean? Normal photographic imaging or profile fitting or spectroscopic work? I really don't think there is lack of good data in either group for the majority of the MilkyWay clusters.

Let me know what you are looking for.

Fridger

[selden]

binary systems in globulars can at best be of interest for fictional applications, since no complete orbital parameter sets have been extracted by astronomers up to now

One of the major uses of cluster generators like MCluster is in the study of how clusters evolve due to gravitational and other effects.

I doubt that much significant information about globular cluster evolution may be obtained without immerging a given cluster model into the gravitational force fields from the parent galaxy! This is standard knowledge. I have heaps of papers about this point.

A galactic gravitational field vector is one of the optional inputs to MCluster.

Certainly there is a lot of simulation progress e.g. with NSTARS using CUDA or similar.

My attempts to generate more realistic clusters have been frustrated by the lack of data. Most cluster star catalogs have been generated from measurements made using CCD images or photographs of clusters' centers. The resulting rectangular clusters aren't particularly realistic or photogenic.

I am puzzled. What kind of data do you mean? Normal photographic imaging or profile fitting or spectroscopic work? I really don't think there is lack of good data in either group for the majority of the MilkyWay clusters.

I'm referring to the coordinates available in the databases at http://www.univie.ac.at/webda/
It's been a few years, but the last time I tried plotting stars associated with the Eagle Nebula (M16, NGC6611), the resulting cluster was square.