Healpix is a tesselation system on the sphere, which depends on a resolution/scale parameter. It provides regular sampling in surface, with no singularity (poles).
The point is to easily get a combined map from sparse data; the result is also scalable in resolution, at least degradation is performed correctly by combining healpix cells.
Cell size (in FoV size, ie in longitude at Equator): scale 6 ~ 1°, 12 ~ 1', 18 ~ 1"
Map projections available with this mode are (in Axes panel) "sin" (i.e.: orthographic), Aitoff (all surface visible, minimize deformations near the poles), and "car" (cylindrical).
In TOPCAT, load a table containing a list of observations located in lon/lat
(working example is a large table of VIRTIS/Rosetta observations of 67P)