\begin{table}%t2
%\centering
\par
\caption{Orbital elements in standard notation.\label{tab:ab}}
\begin{tabular}{ l l  ccc ccc c }
\hline \hline
System &  Author  & $P$, yr & $T$ & $e$ & $a,''$ & $\Omega$, $^\circ$ & $\omega$, $^\circ$  & $i$, $^\circ$  \\
\hline
AB,C & Baize, 1980       & 390.6 & 1716  & 0.27 & 3.95& 142.8& 245.3& 110.2 \\  
A,B & S\"oderhjelm, 1999 & 68.0 & 1998.0 & 0.45 & 0.9 & 125 & 279 & 103 \\ 
A,B & This work    & 67.70 & 1996.805 & 0.513 & 0.912 & 127.5&275.7 & 100.4 \\ 
C,CE & This work, astrom. & 23.7  & 1980.4   & 0.17 &  0.120 & 132  &  171 & 124 \\
 & & $\pm$0.5&   $\pm$1.1& $\pm$0.04 & $\pm$0.004 &  $\pm$10 & $\pm$22 & $\pm$13 \\ 
\hline
\end{tabular}
\end{table}