Version 2.1 A & C of the Celestia extended stars databas
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ElPelado
- Posts: 862
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what dows SQL mean???
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EL XENTENARIO
1905-2005
My page:
http://www.urielpelado.com.ar
My Gallery:
http://www.celestiaproject.net/gallery/view_al ... y-Universe
EL XENTENARIO
1905-2005
My page:
http://www.urielpelado.com.ar
My Gallery:
http://www.celestiaproject.net/gallery/view_al ... y-Universe
Structured Query Language. Its a high level language designed for interacting with databases.
Good luck dr Ganymede let me know how you go in the other thread.
Jamarsa, i still havn't found the time to start playing with linux. Ill make it a priority as eventually I want the game to run under linux as well. Time to get out of this Windows development rut.
It might take a while as I've decided upgrade both my windows and linux systems to make things easier.
Good luck dr Ganymede let me know how you go in the other thread.
Jamarsa, i still havn't found the time to start playing with linux. Ill make it a priority as eventually I want the game to run under linux as well. Time to get out of this Windows development rut.
It might take a while as I've decided upgrade both my windows and linux systems to make things easier.
Marc Griffith http://mostlyharmless.sf.net
Problems with the star Catalog V 2.1A
Rigel, I'm sorry about this, but it seems that there's a problem with your star database (stardb2.1a). 
I've download your catalog (16 MB) file and when I tryied it I noticed an error.
The problem is as follows:
In your catalog the distance of Alpha Centauri pair (ALF Cen A and ALF Cen B) is the same of Proxima Centauri. (4.22 ly). But actually this binary pair is about 4.36 to 4.39 ly away from the Solar System, even though this binary pair belongs to the same stellar system of Proxima Centauri. This kind of error is intolerable for such a bright nearby binary star (mV about -0.1).
This problem seems to be caused by the software that parses the Hipparcos/Tycho catalogues. It seems that this software considers the largest parallax (shortest distance) of the stars that belongs to the same stellar system and uses this parallax for every star of that system.
I belive the correction of this error is relatively simple. One suggestion would be to check the parallax difference of stars belonging to the same system, and preserving their parallax difference if their parallax difference is greater than some value (eg 1 mas), instead of considering the same parallax for stars belonging to the same system.
The standard database distributed with Celestia 1.3.0 (for Windows) also had this problem. (I belive this database is a subset of your more complete database). I've posted a bug notice in Sourceforge about this.
The correct parallax as given by the Hipparcos Catalog are as follows:
Proxima Centauri (HIP 70890) => pi = (772.33 +- 2.42) mas ==> (4.223 =- 0.013) ly
ALF CEN AB (HIP 71683; HIP 71681) => pi = (742.12 +- 1.40) mas ==> (4.395 +- 0.008) ly
P.S: Within a week I'll have more time, and possibly time to contribute to Celestia with some bug fixes, add-ons, etc.
Best Regards,
M?rcio. (Marcio)
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Just some curiosities about the Alpha Centauri System:
ALF CEN A is about 20 to 30 AU far apart from ALF CEN B (they orbit aroud their common barycenter in a period of about 80 years, in an reasonably excentric orbit). In turn, both stars are about .22 ly far apart from Proxima Centauri.
Even though our sun is 4.38 ly far from ALF CEN AB, or about 20 times farther than Proxima Centauri, it's about 40 times brighter than Proxima Centauri, as seen from ALF CEN AB. (It's incredible how red dwarfs are really so dim).
Our solar system is the nearest star system to the Alpha Centauri System (ALF CEN A, ALF CEN B and Proxima Centauri).
The Alpha Centauri System is also the nearest star system to our solar system.
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I've download your catalog (16 MB) file and when I tryied it I noticed an error.
The problem is as follows:
In your catalog the distance of Alpha Centauri pair (ALF Cen A and ALF Cen B) is the same of Proxima Centauri. (4.22 ly). But actually this binary pair is about 4.36 to 4.39 ly away from the Solar System, even though this binary pair belongs to the same stellar system of Proxima Centauri. This kind of error is intolerable for such a bright nearby binary star (mV about -0.1).
This problem seems to be caused by the software that parses the Hipparcos/Tycho catalogues. It seems that this software considers the largest parallax (shortest distance) of the stars that belongs to the same stellar system and uses this parallax for every star of that system.
I belive the correction of this error is relatively simple. One suggestion would be to check the parallax difference of stars belonging to the same system, and preserving their parallax difference if their parallax difference is greater than some value (eg 1 mas), instead of considering the same parallax for stars belonging to the same system.
The standard database distributed with Celestia 1.3.0 (for Windows) also had this problem. (I belive this database is a subset of your more complete database). I've posted a bug notice in Sourceforge about this.
The correct parallax as given by the Hipparcos Catalog are as follows:
Proxima Centauri (HIP 70890) => pi = (772.33 +- 2.42) mas ==> (4.223 =- 0.013) ly
ALF CEN AB (HIP 71683; HIP 71681) => pi = (742.12 +- 1.40) mas ==> (4.395 +- 0.008) ly
P.S: Within a week I'll have more time, and possibly time to contribute to Celestia with some bug fixes, add-ons, etc.
Best Regards,
M?rcio. (Marcio)
------------------------------------------------------------------------------
Just some curiosities about the Alpha Centauri System:
ALF CEN A is about 20 to 30 AU far apart from ALF CEN B (they orbit aroud their common barycenter in a period of about 80 years, in an reasonably excentric orbit). In turn, both stars are about .22 ly far apart from Proxima Centauri.
Even though our sun is 4.38 ly far from ALF CEN AB, or about 20 times farther than Proxima Centauri, it's about 40 times brighter than Proxima Centauri, as seen from ALF CEN AB. (It's incredible how red dwarfs are really so dim).
Our solar system is the nearest star system to the Alpha Centauri System (ALF CEN A, ALF CEN B and Proxima Centauri).
The Alpha Centauri System is also the nearest star system to our solar system.
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chris
- Site Admin
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The Celestia star database tool does indeed set the parallaxes of known companion stars to be equal before computing the distance. Without this adjustment, multiple star systems ended up being separated by light years in the radial direction. For very close stars, the HIPPARCOS parallaxes are accurate enough that modifying them this way is a bad idea . . . Are there any other systems where you've seen this problem?
--Chris
--Chris
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Gennaro
What's the use of adding loads of new stars when even the stellar neighbourhood out to 20 ly is so woefully inaccurate (or so it seems to me)?
Sorry Rigel, you have probably done a great job, but I downloaded your 2.1.A extension and apart from a few Tycho objects added, I couldn't see anything done to remedy the basic misrepresentations, left outs, and inaccuracies.
Sorry Rigel, you have probably done a great job, but I downloaded your 2.1.A extension and apart from a few Tycho objects added, I couldn't see anything done to remedy the basic misrepresentations, left outs, and inaccuracies.
If you want an accurate list of stars out to 25LY, see the forum topic at
http://63.224.48.65/forum/viewtopic.php?t=2594
If you feel that the currently available stars databases are inadequate, you should consider creating more appropriate ones.
http://63.224.48.65/forum/viewtopic.php?t=2594
If you feel that the currently available stars databases are inadequate, you should consider creating more appropriate ones.
Selden
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Gennaro
All I know is that Celestia isn't very correct. I have actually compiled a list of missing and misrepresented stars out to 20 ly, mostly using RECONS web resources, but I had no idea people were already working on these things.
That thread was great and I'd love to help if I only knew how to contribute. To be frank, I'm a total computer illiterate.
That thread was great and I'd love to help if I only knew how to contribute. To be frank, I'm a total computer illiterate.
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granthutchison
- Developer
- Posts: 1863
- Joined: 21.11.2002
- With us: 22 years
I compiled the add-on list Selden pointed you at (using RECONS and a few other sources), and also weeded out and corrected parallaxes for local space in the Celestia stars.dat file - so later versions of Celestia are more accurate than previously.Gennaro wrote:All I know is that Celestia isn't very correct. I have actually compiled a list of missing and misrepresented stars out to 20 ly, mostly using RECONS web resources, but I had no idea people were already working on these things.
So if you combine the current version of Celestia with my add-on stc, things should look a lot better - but let me know if you see anything that still needs fixed.
Grant
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Gennaro
Sure thing! 
That way I could at least make myself and my lately acquired knowledge a little useful.
Pleased to meet you Grant.
Last time I was here, about 6 months ago, no one seemed commited to projects like these or looked very much like demanding scientific precision on the whole, so judge if I'm positively surprised when looking around these forums at present.
Just have to get my recently re-installed Celestia working well. It's very slow at updating, even if I'm using a GeForce II MX 400 graphics card. FAQ's says it's probably a matter of OpenGL. I don't know.
That way I could at least make myself and my lately acquired knowledge a little useful.
Pleased to meet you Grant.
Last time I was here, about 6 months ago, no one seemed commited to projects like these or looked very much like demanding scientific precision on the whole, so judge if I'm positively surprised when looking around these forums at present.
Just have to get my recently re-installed Celestia working well. It's very slow at updating, even if I'm using a GeForce II MX 400 graphics card. FAQ's says it's probably a matter of OpenGL. I don't know.