\begin{table}%t3
 %\centering
\par
 \caption {\label{tab:errors}Masses of objects in the Kuiper belt, as a function of
  the assumed relative accuracy~$\sigma$, with which orbital elements
  of TNOs were deduced from observations.  
}
\begin{tabular}{cccc}
\hline\hline
\noalign{\smallskip}
$\sigma [\%]$ & $M_{\rm CKB}$ & $M_{\rm RES}$ & $M_{\rm CKB+RES}$ \\
\hline 
$5$  & $46.1 \pm 1.6$ & $8.7 \pm 0.6$ & $54.8 \pm 1.7$   \\
$10$ & $48.3 \pm 2.2$ & $9.1 \pm 0.7$ & $57.3 \pm 2.3$   \\
$15$ & $53.3 \pm 3.5$ & $9.7 \pm 0.8$ & $63.0 \pm 3.6$  \\
\hline
\end{tabular}
\tablefoot{Abbreviations and units are as in Table~\ref{tab:mass}.}
\end{table}