I have USNO A2 catalog and it has 6GB in size. The file format of the catalog is .cat. How can i add this catalog or any other .cat catalog to celestia? I see the star catalog from celestia is .dat format.
Anyone knows? There is a program to convert .cat files into celestia .dat files?
Question about adding a star catalog to celestia
There are several problems with trying to use the USNO A2.0 catalog.
You might want to consider the 2 million star Addon instead. See the Motherlode's Stars page at http://www.celestiamotherlode.net/catal ... _stars.php
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Alternatively, if you really want to view the stars shown by large catalogs like this, you might consider using 2D software. Guide, Iris and XEphem are three examples that can use the USNO database.
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1. USNO A2.0 contains no distance values.
Don't forget that Celestia is a 3D application. It requires RA, Dec and distance values. Most star catalogs are only 2D, using RA and Dec values to place stars on the sky, not in space. They don't contain distance values.
There are algorithms that can estimate a star's distance from its luminosity and spectral type, but they are difficult to apply accurately for all cases.
2. It's large, thus slow:
USNO A2.0 contains positions for over 500,000,000 stars. Celestia would run rather slowly with a database that large.
3. It's large, thus needs lots of memory:
Celestia loads all of its star catalog into the computer's main memory. It uses about 50 bytes/star, so for 500 million stars, it'd need about 25 GigaBytes. Few systems have that much. (Smaller systems would have to use virtual memory, thus making Celestia run even slower.) The standard version of Celestia uses 32 bit addressing, so it is limited to about 2GB, maybe 4GB. In principle a 64 bit version of Celestia could be built, but I haven't heard of anyone doing that recently, and I don't know if it would actually be able to access a database that large. Someone would have to debug it.
4. I don't know of any conversion utilities. I'm sure someone would have to write one.
You might want to consider the 2 million star Addon instead. See the Motherlode's Stars page at http://www.celestiamotherlode.net/catal ... _stars.php
[edit]
Alternatively, if you really want to view the stars shown by large catalogs like this, you might consider using 2D software. Guide, Iris and XEphem are three examples that can use the USNO database.
[/edit]
1. USNO A2.0 contains no distance values.
Don't forget that Celestia is a 3D application. It requires RA, Dec and distance values. Most star catalogs are only 2D, using RA and Dec values to place stars on the sky, not in space. They don't contain distance values.
There are algorithms that can estimate a star's distance from its luminosity and spectral type, but they are difficult to apply accurately for all cases.
2. It's large, thus slow:
USNO A2.0 contains positions for over 500,000,000 stars. Celestia would run rather slowly with a database that large.
3. It's large, thus needs lots of memory:
Celestia loads all of its star catalog into the computer's main memory. It uses about 50 bytes/star, so for 500 million stars, it'd need about 25 GigaBytes. Few systems have that much. (Smaller systems would have to use virtual memory, thus making Celestia run even slower.) The standard version of Celestia uses 32 bit addressing, so it is limited to about 2GB, maybe 4GB. In principle a 64 bit version of Celestia could be built, but I haven't heard of anyone doing that recently, and I don't know if it would actually be able to access a database that large. Someone would have to debug it.
4. I don't know of any conversion utilities. I'm sure someone would have to write one.
Selden