\begin{table}%t1
\caption{\label{table:fractions}Fraction of true detections~($f_{\rm t}$) and false detections~($f_{\rm f}$) versus threshold level~$T$ for the convolution-based despiking method, for~the two reference cases~($R_1$ and~$R_2$) (see~text). Here $\langle A \rangle = 10 \sigma$.}
%\centering
\par
\begin{tabular}{ccccc}
\hline \hline \noalign{\smallskip}
 Threshold $T$ & $f_{\rm t} (R_1)$(\%)  &  $f_{\rm f} (R_1)$(\%) & $f_{\rm t} (R_2)$(\%)  &  $f_{\rm f} (R_2)$(\%)\\
\hline  
 0.5$\sigma$ & 37 &  2.9    &  33 &  19  \\
 1$\sigma$    & 27 &  0.3    &  24 & 3.8  \\
 2$\sigma$   & 16 &  0.005  &  13 & 0.02 \\
\hline
\end{tabular}
\end{table}