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HEALPix Pixel Coordinates

Below is a table of FITS files; each file contains a 'skymap' of the latitude and longitude (in degrees) of the center of each HEALPix pixel. The coordinates for each pixel were computed in Galactic coordinates and converted into J2000 Ecliptic and Celestial coordinates; the underlying projection of these maps still assume Galactic reference frame regardless of the coordinate system reported.

The skymaps supplied below assume a Galactic coordinate projection (matching the skymaps provided by the WMAP team). If your skymap was created assuming a native projection in a different coordinate system, use the Galactic coordinate maps below to retrieve the longitude and latitude of each pixel in that coordinate system.

The recommended download procedure for FITS files is to right click on the file name and select save. Left-clicking on a filename may result in the FITS file being displayed in the browser in an unreadable form.

Coordinates are supplied for seven resolution indices: 4--10. HEALPix supports two pixel ordering systems: nested and ring; coordinate maps for both are provided. A table describing the pixel characteristics at each resolution follows.

Nested Pixel Ordering
Res. NSide Galactic Ecliptic Celestial
4 16 pixel_coords_map_nested_galactic_res4.fits pixel_coords_map_nested_ecliptic_res4.fits pixel_coords_map_nested_celestial_res4.fits
5 32 pixel_coords_map_nested_galactic_res5.fits pixel_coords_map_nested_ecliptic_res5.fits pixel_coords_map_nested_celestial_res5.fits
6 64 pixel_coords_map_nested_galactic_res6.fits pixel_coords_map_nested_ecliptic_res6.fits pixel_coords_map_nested_celestial_res6.fits
7 128 pixel_coords_map_nested_galactic_res7.fits pixel_coords_map_nested_ecliptic_res7.fits pixel_coords_map_nested_celestial_res7.fits
8 256 pixel_coords_map_nested_galactic_res8.fits pixel_coords_map_nested_ecliptic_res8.fits pixel_coords_map_nested_celestial_res8.fits
9 512 pixel_coords_map_nested_galactic_res9.fits pixel_coords_map_nested_ecliptic_res9.fits pixel_coords_map_nested_celestial_res9.fits
10 1024 pixel_coords_map_nested_galactic_res10.fits pixel_coords_map_nested_ecliptic_res10.fits pixel_coords_map_nested_celestial_res10.fits
Ring Pixel Ordering
Res. NSide Galactic Ecliptic Celestial
4 16 pixel_coords_map_ring_galactic_res4.fits pixel_coords_map_ring_ecliptic_res4.fits pixel_coords_map_ring_celestial_res4.fits
5 32 pixel_coords_map_ring_galactic_res5.fits pixel_coords_map_ring_ecliptic_res5.fits pixel_coords_map_ring_celestial_res5.fits
6 64 pixel_coords_map_ring_galactic_res6.fits pixel_coords_map_ring_ecliptic_res6.fits pixel_coords_map_ring_celestial_res6.fits
7 128 pixel_coords_map_ring_galactic_res7.fits pixel_coords_map_ring_ecliptic_res7.fits pixel_coords_map_ring_celestial_res7.fits
8 256 pixel_coords_map_ring_galactic_res8.fits pixel_coords_map_ring_ecliptic_res8.fits pixel_coords_map_ring_celestial_res8.fits
9 512 pixel_coords_map_ring_galactic_res9.fits pixel_coords_map_ring_ecliptic_res9.fits pixel_coords_map_ring_celestial_res9.fits
10 1024 pixel_coords_map_ring_galactic_res10.fits pixel_coords_map_ring_ecliptic_res10.fits pixel_coords_map_ring_celestial_res10.fits

The number of pixels in a file is computed from its resolution index (Res).

nside= 2res : The number of pixels per side.
npix= 12 nside2 : The total number of pixels in the map.

HEALPix Pixel Information
Res NSide NPixels Mean Spacing
(deg)
Area
(sterad)
0 1 12 58.6323 1.0471976 X 10+00
1 2 48 29.3162 2.6179939 X 10-01
2 4 192 14.6581 6.5449847 X 10-02
3 8 768 7.3290 1.6362462 X 10-02
4 16 3072 3.6645 4.0906154 X 10-03
5 32 12288 1.8323 1.0226539 X 10-03
6 64 49152 0.9161 2.5566346 X 10-04
7 128 196608 0.4581 6.3915866 X 10-05
8 256 786432 0.2290 1.5978967 X 10-05
9 512 3145728 0.1145 3.9947416 X 10-06
10 1024 12582912 0.0573 9.9868541 X 10-07
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Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason