def _make_bright_pixel_mask(intensity_mean, mask_factor=5.0):
        """ Make of mask of all the brightest pixels """
        mask = np.zeros((intensity_mean.data.shape), bool)
        nebins = len(intensity_mean.data)
        sum_intensity = intensity_mean.data.sum(0)
        mean_intensity = sum_intensity.mean()
        for i in range(nebins):
            mask[i, 0:] = sum_intensity > (mask_factor * mean_intensity)
        return HpxMap(mask, intensity_mean.hpx)