How to generate 20 million stars for a spiral galaxy?

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john71
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john71
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#1by john71 » 12.11.2017, 20:25

This topic is about the MCL2STC cluster generator: link https://celestia.space/forum/viewtopic.php?f=23&t=16494&p=131412&hilit=mcluster#p131412.

How can I create using MCL2STC 20 million stars for a spiral galaxy?

I succeeded creating a cluster with 500 000 stars, but the cluster's shape should be obviously different (spiral-like)...

Cham M
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Cham M
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#2by Cham » 13.11.2017, 00:51

Which spiral galaxy ? At what distance from the Sol ?

And a 20 M_stars STC database would be insane at loading time and memory usage. The Celestia search field would fall to a crawl, i.e. become totally unusable (waaaay too slow, unusable !). I know! I've done it before with a 2 Mstars file only. Launching Celestia will take half an hour, if not much more!

Check these topics :

viewtopic.php?f=23&t=17041&p=131128&hilit=millions+stars#p131128

viewtopic.php?f=23&t=17426&p=134406&hilit=millions+stars#p134406

The 1 million stars STC file for M31 is 145 MB on disk. So a 20 millions stars would be an insane 2900 MB = almost 3 GB text file !
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selden
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#3by selden » 13.11.2017, 12:28

By modern standards, 3GB really isn't particularly large, but, even so, the final on-disk database wouldn't have to be that big.

Celestia doesn't have to use textual STC files. Multiple STC files can be translated into a single binary "stars.dat" which would have much better load-time performance. The 2M stars.dat available from the MotherLode is about 40MB, loads reasonably quickly (< 10 sec on my computer with an SSD system disk) and has good runtime performance. A little more patience would be needed for a 20M 400MB stars.dat to load, but I dunno what Celestia's resulting runtime performance would be. It'd depend on a lot of factors, but I suspect it'd still be acceptable.

I mention multiple STC files because it'd probably be easiest to use different algorithms to generate the different regions comprising a typical spiral galaxy, including the core, thin disk, thick disk and halo.
Selden

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#4by Chuft-Captain » 13.11.2017, 16:41

I wonder if the tools here: https://sourceforge.net/p/celestia/code/HEAD/tree/trunk/celestia/src/tools/stardb/ could be used to convert Cham's Andromeda STC into a DAT file?
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john71
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#5by john71 » 13.11.2017, 21:05

I agree with selden. If stc->dat conversion is possible, then with 400MB data and running the 64 bit version of Celestia it should not be a problem.

By the way in a few years time the ESO-GAIA data (1 billion stars!) will be available, so it is time to start experimenting with huge data files.

Is there any way MCL2STC can be configured to create a generic spiral-like cluster?


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