Optical-MIR diagram along with an isochrone from the Padova library (Marigo et al. 2008). Adopted are an age of 12.59 Gyr, metallicity of Z = 0.004, distance of (m − M)_° = 13.38 and reddening of E_B − V = 0.055. The dashed line marks the RGB tip, while the horizontal branch level is expected at N_8.6   μm ≃ 12.1. Open circles highlight the verified LPVs. The green arrow marks the  ~1000   L_⊙ luminosity level.