What is the license for index files?

[knyipab]

The astrometry.net README says The index files come with their own license conditions. See the file GETTING-INDEXES for details. but I could not find any GETTING-INDEXES file. What exactly is the license for the indexes file such as the 4100 series and 5200 series? Thank you!

[dstndstn]

Oh, that's a good question!

That text is old - the 200-series files were derived from the USNO-B1.0 catalog, which has funny licensing rules that meant we could not make the 200-series files cleanly open-source.

I think later files should be fine to license under some open license. But someone would have to check. The catalogs in question are Tycho-2 and Gaia DR2.

My view is that the Astrometry.net tools do not add any special magic, so I do not want to add any license conditions. But we do need to respect any conditions that exist on the source catalogs.

[knyipab]

Really appreciate your prompt answer!

Indeed, I am trying to bundle 4115-4119 index files as a distro pacakge (https://github.com/termux-user-repository/tur/pull/850), but I have to fill in the license file.

• Gaia seems to come with quite open license: https://www.cosmos.esa.int/web/gaia-users/license
• There does not seem to be license info for Tycho-2

[dstndstn]

Thanks for the Gaia link, that's helpful. The 4100-series are built only from Tycho-2, and unfortunately, the Gaia catalog is missing many stars at the bright end, so Tycho-2 really is required both for 4100 and 5200.

Could you perhaps check whether one of the catalog services like Vizier provides any licensing information?

Astronomers are typically not very exact or explicit about data file licensing -- publicly released data are generally presumed to be free for use, without specifying exactly what that means. And that was even more true back when Tycho-2 was released!

[knyipab]

It seems that license related to Vizier is available at https://cds.u-strasbg.fr/vizier-org/licences_vizier.html but still quite vague.

I understand it is hard to tell the data license from academic paper. I think I may simply take reference to https://github.com/lupinix/astrometry-tycho2/blob/master/LICENSE.txt and make a license file like this:

Copyright 2000 Hog E., Fabricius C., Makarov V.V., Urban S., Corbin T., Wycoff G., Bastian U., Schwekendiek P., Wicenec A. (Tycho-2 catalogue)

Copyright 2006-2015 Michael Blanton, David W. Hogg, Dustin Lang, Keir Mierle and Sam Roweis (scripts to generate 4100-series index files)

See if the second part about astrometry looks good to you. Thanks

[dstndstn]

It sounds like Ole went to the effort of contacting the Tycho-2 author directly and got his confirmation, so I think you are good to go.

For the Astrometry.net team, we only claim copyright on the software that we wrote, not on any of the resulting data files. That copyright statement is fine, I think; you may want to state that the license flows from the Tycho-2 catalog, rather than from the Astrometry.net software.

Thanks for putting in this effort!

[knyipab]

Thanks. Let me be more explicit and put in

The 4100-series index files are generated from and follow the license of the Tycho-2 catalogue. 

The license information for the Tycho-2 catalogue: 
Copyright 2000 Hog E., Fabricius C., Makarov V.V., Urban S., Corbin T., Wycoff G., Bastian U., Schwekendiek P., Wicenec A. 

The Astrometry.net team claims copyright on the script to generate 4100-series index files:
Copyright 2006-2015 Michael Blanton, David W. Hogg, Dustin Lang, Keir Mierle and Sam Roweis

[dstndstn]

Looks great! If you want, you could add,

The Astrometry.net team claims copyright on the script to generate 4100-series index files (but not on the resulting index files):