Here is a new stars database for Celestia
Hello !
I read the recent posts about the extended database. I will make some investigations to see if I can improve the extraction procedure, and generate a new one with lesser distance bugs, at least for Sun's neighborhood.
Some near stars are also missing from the Tycho/Hipparcos catalogs. I've tried to find a database of those stars, and I found one, but the problem is that I should generate a fictious hipparcos/tycho number to enter them in the database, and this could enter in conflict with existing and real numbers...
I read the recent posts about the extended database. I will make some investigations to see if I can improve the extraction procedure, and generate a new one with lesser distance bugs, at least for Sun's neighborhood.
Some near stars are also missing from the Tycho/Hipparcos catalogs. I've tried to find a database of those stars, and I found one, but the problem is that I should generate a fictious hipparcos/tycho number to enter them in the database, and this could enter in conflict with existing and real numbers...
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chris
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That would be great . . . Also, I need to resurrect my project to constrain the distances of stars know to be members of clusters.Rigel wrote:Hello !
I read the recent posts about the extended database. I will make some investigations to see if I can improve the extraction procedure, and generate a new one with lesser distance bugs, at least for Sun's neighborhood.
Rigel wrote:Some near stars are also missing from the Tycho/Hipparcos catalogs. I've tried to find a database of those stars, and I found one, but the problem is that I should generate a fictious hipparcos/tycho number to enter them in the database, and this could enter in conflict with existing and real numbers...
This is a pretty serious limitation of the current numbering system . . . How do we assign unique numbers to stars from different catalogs? Additionally, it would be nice to be use different catalog numbers for existing stars instead of having HIPPARCOS, HD, and the Tycho catalogs hardcoded. I don't have a solution yet, but I'm working on it . . .
--Chris
Hello Chris, hello everybody interested in this topic !
I have made some investigations to find information and databases of nearby stars that could be used.
Clearly, the problem in the current stars database of Celestia is its incompletness within 25 pc. A lot of faint stars (like Wolf 359 !) are missing because they are neither in the Hipparcos catalog nor in the Tycho one. Hipparcos is complete up to mv = 12. Wolf 359 has a visual magnitude of 13.45 !
So, in a first step, I could generate a new extended database which will avoid to place non Hipparcos giants stars (class III stars) within 25 pc of the Sun, or convert them into class V stars (this is more probable for those stars). This is quite easy to do.
But, the incompletness problem will still remain.
The only database that could be used to complete Celestia seems to be the 3rd Version of the Gliese Catalog of nearby stars (1991). Gliese 3 contains about 3803 stars (all known stars in 1991 within 25 pc of the Sun). But also in this catalog, some parallaxes are photometric ones with bad precision.
Another catalog project of nearby stars within 25 pc is the NStars database (http://nstars.arc.nasa.gov/index.cfm), but the catalog itself seems to be only accessible through web queries. And as stated by them :
<< The total number of stars within 25 pc (scaled from the better-known sample within 5 pc) is expected to be at least 7500, but only ~2600 objects are presently known to that distance. Thus the catalog is now only about 30% complete. In addition, substellar objects are being found rapidly enough that their total space density may be comparable to stars. Planets and brown dwarfs will be included in the NStars database. >>
So, you can see that the problem of the completness and accuracy within 25 pc is not an easy one, even for the scientific community.
Thus, the only solution seems for the moment to complete Celestia stars database with stars that come from the Gliese 3 catalog. And Chris, the current numbering system of Celestia could still be used, because it remains a huge amount of numbers that aren't used.
But there are still other problems and I have to look if and how they can be solved...
Have a good week-end
Pascal
I have made some investigations to find information and databases of nearby stars that could be used.
Clearly, the problem in the current stars database of Celestia is its incompletness within 25 pc. A lot of faint stars (like Wolf 359 !) are missing because they are neither in the Hipparcos catalog nor in the Tycho one. Hipparcos is complete up to mv = 12. Wolf 359 has a visual magnitude of 13.45 !
So, in a first step, I could generate a new extended database which will avoid to place non Hipparcos giants stars (class III stars) within 25 pc of the Sun, or convert them into class V stars (this is more probable for those stars). This is quite easy to do.
But, the incompletness problem will still remain.
The only database that could be used to complete Celestia seems to be the 3rd Version of the Gliese Catalog of nearby stars (1991). Gliese 3 contains about 3803 stars (all known stars in 1991 within 25 pc of the Sun). But also in this catalog, some parallaxes are photometric ones with bad precision.
Another catalog project of nearby stars within 25 pc is the NStars database (http://nstars.arc.nasa.gov/index.cfm), but the catalog itself seems to be only accessible through web queries. And as stated by them :
<< The total number of stars within 25 pc (scaled from the better-known sample within 5 pc) is expected to be at least 7500, but only ~2600 objects are presently known to that distance. Thus the catalog is now only about 30% complete. In addition, substellar objects are being found rapidly enough that their total space density may be comparable to stars. Planets and brown dwarfs will be included in the NStars database. >>
So, you can see that the problem of the completness and accuracy within 25 pc is not an easy one, even for the scientific community.
Thus, the only solution seems for the moment to complete Celestia stars database with stars that come from the Gliese 3 catalog. And Chris, the current numbering system of Celestia could still be used, because it remains a huge amount of numbers that aren't used.
But there are still other problems and I have to look if and how they can be solved...
Have a good week-end
Pascal
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Guest
Hi !
I've checked giant class III stars within 25 pc, and I think now that this could be seen as a borderline error (sorry for the word, I don't know how to translate exactly what I mean in english) of the extraction procedure. Don't forget that the extraction procedure of Tycho stars is precise at 45% on distance for the version 2.0C ! But I don't think that this could be a systematic error of the extraction and interpolation procedure itself.
The only solution seems to be to integrate the Gliese catalog only (for stars within 25 pc that aren't referenced in the Hipparcos catalog) to get a quite accurate representation of our solar system's neighborhood.
I've checked giant class III stars within 25 pc, and I think now that this could be seen as a borderline error (sorry for the word, I don't know how to translate exactly what I mean in english) of the extraction procedure. Don't forget that the extraction procedure of Tycho stars is precise at 45% on distance for the version 2.0C ! But I don't think that this could be a systematic error of the extraction and interpolation procedure itself.
The only solution seems to be to integrate the Gliese catalog only (for stars within 25 pc that aren't referenced in the Hipparcos catalog) to get a quite accurate representation of our solar system's neighborhood.