pixel_resolution_to_nside

astropy_healpix.pixel_resolution_to_nside(resolution, round='nearest')

Find closest HEALPix nside for a given angular resolution.

This function is the inverse of nside_to_pixel_resolution, for the default rounding scheme of round='nearest'.

If you choose round='up', you’ll get HEALPix pixels that have at least the requested resolution (usually a bit better due to rounding).

Pixel resolution is defined as square root of pixel area.

Parameters:

resolutionQuantity

Angular resolution

round{‘up’, ‘nearest’, ‘down’}

Which way to round

Returns:

nsideint

The number of pixels on the side of one of the 12 ‘top-level’ HEALPix tiles. Always a power of 2.

Examples

>>> from astropy import units as u
>>> from astropy_healpix import pixel_resolution_to_nside
>>> pixel_resolution_to_nside(13 * u.arcmin)
256
>>> pixel_resolution_to_nside(13 * u.arcmin, round='up')
512