\begin{table}%T6
%\centering
\small
\caption{Clusters with the largest absolute populations of blue 
stragglers ($N_{\rm BS} \geq 20$).}
\label{tab:nabsoluta}
\begin{tabular}{lcc|lcc} \hline\hline
Cluster & $\log \textup{(age)}$ & $N_{\rm BS}$ &
Cluster & $\log \textup{(age)}$ & $N_{\rm BS}$ \\
\hline 
\object{Berkeley 18}  &  9.6  & 126 &
\object{Berkeley 17}  &  10.1 &   31 \\ 
\object{Berkeley 14} & 9.2 &    94 &
\object{King 2}   &   9.8  &  30 \\  
\object{NGC 6791}   &   9.6  &   75 &
\object{Pismis 3}    &   9.0 &    30 \\
\object{Berkeley 66}   &  9.7 &  70 &
\object{NGC 6819}   &     9.2 &   29 \\
\object{Trumpler 5}  &  9.6 &  70  & 
\object{Collinder 110} &     9.2 &    27 \\
\object{Berkeley 70} & 9.7 & 64 &
\object{King 11}    &   9.2  &   27 \\
\object{Ruprecht 46}  &   9.6 &   62 &
\object{NGC 6253}  &   9.7  &  27  \\
\object{Collinder 261} &    10.0 &  54  &
\object{NGC 188} & 9.6 &  24  \\
\object{Berkeley 21}  &  9.3 & 51 &
\object{NGC 1798}    &  9.2 &  24  \\  
\object{Pismis 2}    &    9.1 &   46 &  
\object{NGC 2141}   &  9.2  &  24 \\
\object{Berkeley 39}   &  9.9  &  43 &  
\object{NGC 2682}    &   9.4 &  30 \\  
\object{NGC 2158}   &   9.0 & 40 &
\object{NGC 7789}    & 9.2  &   22 \\
\object{Berkeley 32}   &  9.5 &   37 &
\object{Berkeley 22}  &   9.0 &   21  \\
\object{NGC 7142}   &  9.3  &   37 &
\object{Berkeley 31}   &  9.3 &  20 \\
\object{Melotte 66}   &  9.5 &    35  & & & \\
\hline
\end{tabular}
\end{table}