Left panel: HRD of RGB of NGC 1261, with RGBb stars highlighted in orange and by a blue dashed line referring to the RGBb luminosity obtained from the fit. The errors on log L_RGBb already include the systematics due to the number of RGB stars (see Appendix B) and the distance modulus (Baumgardt & Hilker 2018). Right panel: KDE (light blue zone) of luminosity distribution (lower labels) and relative fit (orange line). The blue line represents the histogram of the RGB luminosity with Poissonian errors (upper labels).