April 25, 2026
Squares vs hexes showdown
HEALPix
The cosmic map slicing the sky into equal tiles—fans pick sides in the squares vs hexes showdown
TLDR: HEALPix divides the sky into equal tiles for astronomy maps. Commenters praise its indexing, compare it to Uber’s H3 hex grid, and shout out healpy and HiPS—showing that how we slice spheres shapes everything from space surveys to location apps
Space nerds are vibing over HEALPix—the adorably precise way astronomers slice the sky into equal tiles. Fans say it’s not just for cosmic microwave background maps; it’s a killer index, “super useful for indexing… like geohashes,” cheers sligbad. Others are dropping tool links: healpy for Python tinkerers and HiPS for zoomable sky maps. Translation for non-astronomers: HEALPix is the system that chops the whole sky into equal chunks so scientists can compare apples to apples.
The spicy subplot? Shape supremacy. When ahurmazda saw Uber’s H3 hex grid, it “really reminded me of healpix”—cue a friendly feud: squares for the cosmos, hexes for city streets. Meanwhile, kmaitreys casually flexes a summer project to “find void galaxies,” spawning jokes about mapping the void in our love lives. Commenters paint HEALPix as the quiet OG: mature, standardized (it even has its own FITS file tag, HPX), and fast at mathy sky tricks—while H3 is the flashy urban cousin. The vibe is playful but pointed, with folks trading zoom demos, war stories from grad school, and hot takes about which grid rules the world. Verdict from the comments: whether you’re charting galaxies or delivery routes, the way you slice the sphere is everything—and HEALPix still has gravity
Key Points
- •HEALPix is a hierarchical equal-area pixelisation algorithm and projection class for mapping the 2-sphere to the plane, devised in 1997 by Krzysztof M. Górski.
- •The commonly used H=4, K=3 HEALPix projection maps the sphere to 12 square facets, then recursively subdivides them into equal-area pixels.
- •HEALPix combines the Lambert cylindrical equal-area projection (equatorial) with an interrupted Collignon projection (polar) and supports efficient spherical harmonic transforms.
- •HEALPix is implemented in software, represented by the HPX keyword in the FITS standard, and was approved in the FITS WCS by the IAU FITS Working Group in 2006.
- •It is widely used in cosmology (e.g., CMB maps) and by the Gaia mission; alternatives include HTM and the Quadrilateralized Spherical Cube.