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)
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
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.
Fridger
