\begin{table}%t6
  %\centering
\par
    \caption {\label{tab:NGC6397}Derived effective temperatures from empirical calibrations
      of photometry ($(b-y)$ and $(v-y)$), and spectroscopy (Korn et~al. \cite{Korn07}), as well as 
      our theoretical calibration, for groups of stars in the metal-poor cluster NGC~6397. The 
      temperatures are mean values for a number of stars/models in each group.}
    \begin{tabular}{cccccc}
      \hline \hline
                        & Phot.   &         & Spec. & MARCS  &                \\
      $T_{\rm eff}$~[K] & $(b-y)$ & $(v-y)$ &       &$(b-y)$ & $(v-y)$        \\
      \hline	                          
      hRGB              & 5121    &  5132   & 5130  & 5225  &  5226  \\
      lRGB              & 5455    &  5408   & 5456  & 5541  &  5535  \\
      SGB               & 5797    &  5824   & 5805  & 5839  &  5853  \\
      TOP               & 6229    &  6214   & 6254  & 6288  &  6281  \\
      \hline                                          
      $\Delta$(TOP-RBG) & 1108    &  1081   & 1124  & 1063  &  1055  \\
      $\Delta$(TOP-SGB) & 433     &  390    & 449   & 449   &  428   \\
      \hline
    \end{tabular}
  \end{table}