Readable .dat files?

[Reiko]

Thank you jogad for your help, it's greatly appreciated.

What I have been trying to do is convert these giant STC files that I use to place stars in the small and large magellanic clouds into .dat files. Then I wanted to merge those .dat files with celestia's stars.dat so there will only be one file to load at start up.
I don't really know the star count of each STC file but it's probably close to 100,000 for each file. I made them using the globular cluster generator.

[chris]

Just a few short questions/suggestions on making a stars.dat for an addon.

I have also a huge load of data that I am currently converting to .STCs (~1200 entries [without a load of binaries])

Do I really need to assign them a HIP number?

HIP numbers are not required for stars defined in STC files.

I have the data in an X Y Z coordinate system, but I am not sure, if it is the same as used in Celestia. I tried to look that one up, but didn't find its center and orientation (yet).
Can I also define barycenters?

The center of the coordinate system is the solar system barycenter. It is oriented so that the xz-plane is aligned with the ecliptic of epoch J2000.0. The y-axis points northward. The x-axis points out along the ascending node of the plane of the Earth's orbit and the Earth's equator at J2000. This differs from the 'conventional' ecliptic frame by a rotation of 90 degrees about the x-axis.

So, from these questions I'd like to edrive the following feature requests for future Celestia versions:

• Possibility to add user .dat files (binary or text) with addons
• define barycenters
• Possibility to use modify commands for already existing stars within these .dat files

What would be the difference between these dat files and the existing stc format? The binary encoding?

--Chris

[Hungry4info]

What would be the difference between these dat files and the existing stc format? The binary encoding?

Yes, indeed.

[Guckytos]

Just a few short questions/suggestions on making a stars.dat for an addon.

I have also a huge load of data that I am currently converting to .STCs (~1200 entries [without a load of binaries])

Do I really need to assign them a HIP number?

HIP numbers are not required for stars defined in STC files.

I have the data in an X Y Z coordinate system, but I am not sure, if it is the same as used in Celestia. I tried to look that one up, but didn't find its center and orientation (yet).
Can I also define barycenters?

The center of the coordinate system is the solar system barycenter. It is oriented so that the xz-plane is aligned with the ecliptic of epoch J2000.0. The y-axis points northward. The x-axis points out along the ascending node of the plane of the Earth's orbit and the Earth's equator at J2000. This differs from the 'conventional' ecliptic frame by a rotation of 90 degrees about the x-axis.

So, from these questions I'd like to edrive the following feature requests for future Celestia versions:

• Possibility to add user .dat files (binary or text) with addons
• define barycenters
• Possibility to use modify commands for already existing stars within these .dat files

What would be the difference between these dat files and the existing stc format? The binary encoding?

--Chris

Hi chris,

well, I don't know for other SciFi projects, but my input data for the stars comes in X, Y, Z coordinates (a galactic core centered one). So at the moment I have to move the center of the coordinate system, translate the data into galactic coordinates and then the the galactic coordinates into normal RA, Dec, Dist.
If I could just use Celestias X, Y, Z coordinates, this would be a lot easier, only move the origin and then apply a rotation, so that the origins match, and assign the correct name and spectral type.

And the HIP numbers question was meant for the *.dat file. I know that I don't need it anymore for *.stc, luckyly.

So, this would be a nice feature. But probably also a troublesome. You would have to integrate checks for double definitions of stars, take into account that two different addons could try to alter a stars definition and so on. And then give concise error messages that tell which lines in which *.dat collide. Hmmm, probably too much much trouble at the moment.

Best regards,

Guckytos

[ajtribick]

Celestia's XYZ coordinates are in the ecliptic coordinate system IIRC...

[Reiko]

What would be the difference between these dat files and the existing stc format? The binary encoding?

--Chris

A dat file with 2,000,000 stars loads faster than an stc file with 100,000 stars.

[jdavies]

I'm working on a utility that I think will meet your needs. You can define a star (solar system objects will come next) in an XML text format and then the utility will compile a stars.dat file for you. I wanted to do the same thing. Sometimes I want to view real star information (the Hipparcos info) and sometimes I want to view a fictitious universe.

To see an initial sample of what the text file would look like, check out my post at http://www.shatters.net/forum/viewtopic.php?f=6&t=13277&st=0&sk=t&sd=a&start=15. I don't have the utility done yet, but I hope to have a crude version working by next week. I'm interested in gathering feedback from potential users of the utility, so feel free to post comments and suggestions.

- Jeff