Peak frequency vs. effective temperature for our sample of RGB (red and green symbols) and RC (bluesymbols) stars in NGC6791 and NGC6819, respectively. Circles and squares indicate stars with theeffective temperature taken from the APOKASC catalogue and derived from polynomial fits (greydashed and dotted lines), respectively. Horizontal grey lines represent the uncertainties in T_eff. The inset shows the metallicity measurements from the APOKASC catalogue along with the average values (dashed lines) and their uncertainties (dashed-dotted lines).