CosmoCoffee

After suggestions from the Toruń cosmology group 18 months ago:

http://cosmo.torun.pl/pipermail/cosmo-torun/

that the WMAP data should be readable using free software (free as in speech - http://www.gnu.org) and hence that having a non-free licence for the official healpix software package was not very constructive, it seems that the official group have finally accepted peer pressure and released their package under the GPL:

http://sourceforge.net/projects/healpix/ (version 2.00)

# License: GNU General Public License (GPL)

- click on download to download the package

For anyone interested in what the healpix projection/pixelisation is all about, you can read the following three articles, chronologically:

• astro-ph/0409533
• astro-ph/0409513
• astro-ph/0412607 - updated version: http://www.atnf.csiro.au/people/mcalabr ... 0050615.ps

(For the curious: the chronology of 0409533 and 0409513 is correct: 0409533 was written first, sent to the other group of authors with a proposal for coauthorship, who responded by publishing 0409513 independently without any warning - anyway, the important thing is that the algorithm is clearly documented and public.)

More importantly, in astro-ph/0412607 we point out that the healpix projection/pixelisation is a combined cylindrical equal-area projection + a Collignon (1865) projection, followed by the hierarchical pixelisation of 12 squares. (There's also a generalisation of this class of projections in the paper.)

And there are at least three independent GPL software packages:

• http://sourceforge.net/projects/healpix/ - the official group
• http://cosmo.torun.pl/GPLdownload/dodec ... .12.tar.gz - isolat - a tiny GPL autoconf'ed package, can be included as a fortran77 or C library in any GPL-compatible package, or can be used on the command line with standard gnu/linux type options
• ftp://ftp.atnf.csiro.au/pub/software/wc ... lib.tar.gz wcslib - a complement to the standard fitsio package

So the projection is now well understood and there are several GPL versions of the software. :)))

All's well that ends well.

Does anyone know if there's a forum for discussing improvements or additions to Healpix?

David Larson wrote:Does anyone know if there's a forum for discussing improvements or additions to Healpix?

There isn't any official forum, if that's what you are asking for. But if you have any specific suggestions in mind, I would think sending an email to Eric Hivon and/or Kris Gorski would be a natural approach. Or you could of course always post it in this forum -- somebody is sure to pick it up here.