lonlat_to_healpix

astropy_healpix.lonlat_to_healpix(lon, lat, nside, return_offsets=False, order='ring')

Convert longitudes/latitudes to HEALPix indices

Parameters:

lon, lat : Quantity

The longitude and latitude values as Quantity instances with angle units.

nside : int

Number of pixels along the side of each of the 12 top-level HEALPix tiles

order : { ‘nested’ | ‘ring’ }

Order of HEALPix pixels

return_offsets : bool, optional

If True, the returned values are the HEALPix pixel indices as well as dx and dy, the fractional positions inside the pixels. If False (the default), only the HEALPix pixel indices is returned.

Returns:

healpix_index : int or ndarray

The HEALPix indices

dx, dy : ndarray

Offsets inside the HEALPix pixel in the range [0:1], where 0.5 is the center of the HEALPix pixels