Function to provide the resolution parameter ${N_{\rm side}}$ correspoonding to ${N_{\rm pix}}$ pixels over the full sky.

Location in HEALPix directory tree: src/f90/mod/pix_tools.f90

FORMAT

name & dimensionality	kind	in/out	description

npix	I4B	IN	the number ${N_{\rm pix}}$ of pixels over the whole sky.
var	I4B	OUT	the parameter ${N_{\rm side}}$ . If ${N_{\rm pix}}$ is valid (12 times a power of 2 in $\{1,\ldots,8192\}$ ), ${N_{\rm side}}=\sqrt{{N_{\rm pix}}/12}$ is returned; if not, an error message is issued and -1 is returned.

nside= npix2nside(786432)

Returns the resolution parameter ${N_{\rm side}}$ (256) corresponding to 786432 pixels on the sky.

nside2npix: returns the number of pixels ${N_{\rm pix}}$ correspondinng to resolution parameter ${N_{\rm side}}$

Eric Hivon 2010-06-18

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