\begin{table}%t2
\par
\caption{\label{tab:res}Root mean square deviations of line ratios (R1 is [OI]/[NII], R2 is [SII]/[OI])
     obtained with simulations of increasing resolution.} 
  \small%\centering
\par
  \begin{tabular}{c|c|c|c|c|c|c}
  \hline\hline
    {\bf Sim.} & \multicolumn{2}{|c|}{n2e4b300v50} &  \multicolumn{2}{|c}{n5e4b100v40} & 
    									 \multicolumn{2}{|c}{n5e4b500v55} \\
    \hline
        ref. levs.     &  \multicolumn{1}{|c}{R1} & \multicolumn{1}{c|}{R2} &  \multicolumn{1}{|c}{R1} & \multicolumn{1}{c|}{R2}& \multicolumn{1}{|c}{R1} & \multicolumn{1}{c}{R2} \\
    \hline 
    base--2 & 0.1378 & 0.0319 & 0.1240 & 0.0477 & 0.1150 & 0.0477 \\
    2--4    & 0.0512 & 0.0171 & 0.0883 & 0.0534 & 0.0884 & 0.0499 \\
    4--6    & 0.0141 & 0.0816 & 0.0425 & 0.0418 & 0.0589 & 0.0509 \\
    6--8    & 0.0110 & 0.0141 & 0.0088 & 0.0145 & 0.0256 & 0.0359 \\
    8--10   & 0.0004 & 0.0008 & 0.0017 & 0.0023 & 0.0033 & 0.0084 \\
    \hline
  \end{tabular}
\end{table}