[fitsbits] HEALPIX fits files

[Wayne Landsman]

Eric Greisen wrote:
> AIPS cannot handle HEALPIX but can someone ?

There is FORTRAN, C and IDL code for reading HEALPIX FITS files 
available by registering at http://www.eso.org/science/healpix/.   There 
is also a IDL image display program MAPVIEW available from the WMAP 
software library (http://lambda.gsfc.nasa.gov/product/map/m_sw.cfm). 
  This can be run without an IDL license using the IDL virtual machine 
although this is somewhat cumbersome.

Calabretta & Greisen (2002, A&A, 395, 1077) originally described HealPix 
as a pixelization which defines a distribution of points on the sphere 
but which  does not relate these to points in a plane of projection and 
which therefore is outside the scope of WCS.  But I was excited to see 
Mark Calabretta's recent preprint "Mapping on the HealPix Grid" 
available at astro-ph/0412607 which shows that Healpix *is* associated 
with a map projection, which will incorporated in V3.7  (not yet 
released?) of WCSLIB.    I think this should eventually allow 
astronomical display programs (DS9, AIPS) to convert Healpix maps to any 
desired projection.

The LAMBDA data center plans to increase its use of Healpix FITS files 
for  CMB data, so it would be nice if these files were readable by the 
major display programs.

--Wayne Landsman