def vec2ang(vectors, lonlat=False):
    """Drop-in replacement for healpy `~healpy.pixelfunc.vec2ang`."""
    x, y, z = vectors.transpose()
    rep_car = CartesianRepresentation(x, y, z)
    rep_sph = rep_car.represent_as(UnitSphericalRepresentation)
    return _lonlat_to_healpy(rep_sph.lon.ravel(), rep_sph.lat.ravel(), lonlat=lonlat)