Celestia Forums

Hi :
I am new to celestia and I am using version 1.3.2
I want to create a fictional system with many O type star circulating around a black hole. I am confused with the many configuration files. The .ssc are more or less self explained. My questions are:
1.- what is in stars.dat?
2.- From where does celestia grab the star type,Luminnusity ,etc ?
3.- Can I remove all default stars and other object and create an installation with only my n fictional objects (which are not named hipparcos nor in any other catalog)?
4.- Do I need .stc files to describe the circulating stars or should I use one .sscfile?

rabuter wrote: 1.- what is in stars.dat?

Star data.

rabuter wrote: 2.- From where does celestia grab the star type,Luminnusity ,etc ?

From stars.dat.

rabuter wrote: 3.- Can I remove all default stars and other object and create an installation with only my n fictional objects (which are not named hipparcos nor in any other catalog)?

In recent versions of Celestia you should be able to start up without stars.dat, and display only the stars you've defined in your own stc files. This feature was requested some time ago and (I think) was added to Celestia's capabilities.

rabuter wrote: 4.- Do I need .stc files to describe the circulating stars or should I use one .sscfile?

At present, you'll need an stc for the black hole and will have to added the orbiting stars as Emissive objects defined in an ssc.

Grant

many thanks for your prompt and helpfull reply.
I will try as you say , without stars.dat and with a .stc for the black hole and a .ssc for the many stars.
I am wondering what the GUI will do in the select star option. I expect it will display just the ones I defined in the .ssc file.


Just to be more clear,
Do you know what is the format of the stars.dat?

It puzzle me because It is not an ASCII file but at the same time the starsname.dat is an ascii file where I see there are stars numbers and names.

Is there any relation between the two files?

Should I worry about those two files for my fictional simulation

many thanks,
Robetrto Abuter

granthutchison wrote:

rabuter wrote: 1.- what is in stars.dat?

Star data.

rabuter wrote: 2.- From where does celestia grab the star type,Luminnusity ,etc ?

From stars.dat.

rabuter wrote: 3.- Can I remove all default stars and other object and create an installation with only my n fictional objects (which are not named hipparcos nor in any other catalog)?

In recent versions of Celestia you should be able to start up without stars.dat, and display only the stars you've defined in your own stc files. This feature was requested some time ago and (I think) was added to Celestia's capabilities.

rabuter wrote: 4.- Do I need .stc files to describe the circulating stars or should I use one .sscfile?

At present, you'll need an stc for the black hole and will have to added the orbiting stars as Emissive objects defined in an ssc.

Grant

rabuter wrote:Just to be more clear,
Do you know what is the format of the stars.dat?

If you check the README file, you'll find it says:

The stars.dat file is a binary database of stars, processed from the 50+ meg
HIPPARCOS data set. The first four bytes are an integer (int) value
containing the number of stars in the database. Following that are a bunch of
records of this form:
4 byte int : catalog number
4 byte float : right ascension
4 byte float : declination
4 byte float : parallax
2 byte int : apparent magnitude
2 byte int : stellar class
1 byte : parallax error

Don't get too involved in decoding stars.dat, though ... the format is undergoing a revision for the next release of Celestia.

rabuter wrote:It puzzle me because It is not an ASCII file but at the same time the starsname.dat is an ascii file where I see there are stars numbers and names.

Is there any relation between the two files?

Starnames.dat provides star names linked to the Hipparcos numbers listed in stars.dat. Because stars.dat is a big file consisting entirely of numbers, there are significant benefits in size-reduction to be derived from storing the data as binary rather than text.

rabuter wrote: Should I worry about those two files for my fictional simulation

You can make your simulation without any reference to these files.

Grant

many thanks for the detailed reply. Very clear.
I will proceed with my example. I like very much what I have seen from celestia so far. I hope it will be able to cope with my example ( black hole + orbiting stars ).
Roberto Abuter

granthutchison wrote:

rabuter wrote:Just to be more clear,
Do you know what is the format of the stars.dat?

If you check the README file, you'll find it says:

The stars.dat file is a binary database of stars, processed from the 50+ meg
HIPPARCOS data set. The first four bytes are an integer (int) value
containing the number of stars in the database. Following that are a bunch of
records of this form:
4 byte int : catalog number
4 byte float : right ascension
4 byte float : declination
4 byte float : parallax
2 byte int : apparent magnitude
2 byte int : stellar class
1 byte : parallax error

Don't get too involved in decoding stars.dat, though ... the format is undergoing a revision for the next release of Celestia.

rabuter wrote:It puzzle me because It is not an ASCII file but at the same time the starsname.dat is an ascii file where I see there are stars numbers and names.

Is there any relation between the two files?

Starnames.dat provides star names linked to the Hipparcos numbers listed in stars.dat. Because stars.dat is a big file consisting entirely of numbers, there are significant benefits in size-reduction to be derived from storing the data as binary rather than text.

rabuter wrote: Should I worry about those two files for my fictional simulation

You can make your simulation without any reference to these files.

Grant