\begin{table}%t3
\caption{Electron temperature indicators in \ngc.\label{tab3}}
%\centerline
{\begin{tabular}{lcccc}
\hline
\hline
Ion & Ioniz. & Lines& Observed & $T_{{\rm e}}$\\
 & Pot. (eV)& used &ratio  & (K) \\
\hline
\ion{[N}{ii]} & 14.5 & 5755/6584 & 0.0055 & 6700\\
\ion{[N}{ii]} & 14.5 & 6584/122 & 128. & 6900\\
\ion{[S}{iii]} & 23.3 & 6312/18.7 & 0.0175 & 7900 \\
\ion{[Ar}{iii]} & 27.8 & 7136/8.99 & 0.83 & 8700\\
\ion{[O}{iii]} & 35.1 & 4363/5007 & 0.0175 & 13~700\\
\ion{[O}{iii]} & 35.1 & 5007/51.8  & 3.3 & 7700\\
\ion{[Ne}{iii]} & 41.0 & 3868/15.5 & 0.84 & 10~800\\
\hline
\end{tabular}}
\par
\smallskip
%The ":'' indicate uncertain observations.
\end{table}