\begin{table}%t1
%\centering
\par
\caption{Number of data pairs, after applying stability criteria to the PMT anode currents and to the trigger rates. Single Pointing (SP),
Doubling Pointing (DP), and Single Pointing with Veto (SPV) are explained in the text. The fraction of the data set with a cosmic ray
trigger rate below 15~Hz, which we ascribe to seasonal increases in atmospheric extinction, is also listed. \label{datatab}}
\begin{tabular}{ccccccc}
\hline\hline
    Source	 &     SP  &    DP      &  SPV   &  All pairs & $<$15 Hz &   On hours  \\ \hline
 Mrk~421         &     61  &    44      &  28    &	133   & 20\%    &   38.9      \\ 
 Mrk~501	 &     10  &    25      &  --    &       35   & 50\%    &   10.3      \\ 
 1ES~1426+428     &     --  &    --      &  33    &       33   & 40\%    &    8.8      \\  
 \hline
\end{tabular}
\end{table}