healpy.fitsfunc.read_alm(filename, hdu=1, return_mmax=False)

Read alm from a fits file.

In the fits file, the alm are written with explicit index scheme, index = l**2+l+m+1, while healpix cxx uses index = m*(2*lmax+1-m)/2+l. The conversion is done in this function.

filenamestr or HDUList or HDU or pathlib.Path instance

The name of the fits file to read

hduint, or tuple of int, optional

The header to read. Start at 0. Default: hdu=1

return_mmaxbool, optional

If true, both the alms and mmax is returned in a tuple. Default: return_mmax=False

alms[, mmax]complex array or tuple of a complex array and an int

The alms read from the file and optionally mmax read from the file