\begin{table}%t1
\par
\caption{\label{tab_ringparam}Parameters of an averaged orbit representing the main-belt perturbation as determined from the perturbation on the inner planets.}
\small%\centering
\par
\begin{tabular}{l c c c c c c}
\hline
\hline\noalign{\smallskip}
Planet & $a'$ [AU] & $e'$ & $\varpi'$ [$^{\circ}$] & $I'$ [$^{\circ}$] & $\Omega'$ [$^{\circ}$]\\
\hline
Mars  & 2.71 & 0.04 & $-$1.30 & 0.96 & $-$60.34 \\
Earth & 2.74 & 0.04 & $-$4.88 & 0.89 & $-$50.31 \\
Venus & 2.75 & 0.04 & $-$4.03 & 0.89 & $-$51.08 \\
Mercury & 2.75 & 0.04 & $-$5.71 & 0.88 & $-$50.67 \\
\hline 
\end{tabular}
\end{table}