\begin{table}%t3
\caption{Summary of model atoms used in the disk model calculations. For
  each ion we list the number of NLTE~levels and the number of line
  transitions. In brackets we give the number of lines in the wavelength
  range covered by our optical spectra after fine-structure splitting for
  detailed line-profile calculations.}\label{levels_tab}
%\centering
\par
\begin{tabular}{c c c c}
      \hline
      \hline
Element & Ion & NLTE levels & Lines\\
 \hline
      H  & \scriptsize I          & 10 & 45 (8) \\
         & \mbox{\scriptsize II}  & 1  & --  \\ 
      He & \scriptsize I          & 29 & 61 (16) \\
         & \mbox{\scriptsize II}  & 14 & 91 (14) \\ 
         & \mbox{\scriptsize III} & 1  & --  \\ 
      C  & \mbox{\scriptsize I  } & 7  & 4   (0)\\
         & \mbox{\scriptsize II}  & 38 & 160 (42)\\
         & \mbox{\scriptsize III} & 58 & 329 (143)\\
         & \mbox{\scriptsize IV}  & 9  & 17  (2)\\
         & \mbox{\scriptsize V}   & 1  & --  \\
      O  & \mbox{\scriptsize I  } & 1  & -- \\
         & \mbox{\scriptsize II}  & 29 & 82 (56) \\
         & \mbox{\scriptsize III} & 36 & 42 (47) \\
         & \mbox{\scriptsize IV}  & 11 & 5  (0) \\
         & \mbox{\scriptsize V}   & 6  & 4  (0)\\
         & \mbox{\scriptsize VI}  & 1  & --  \\
      Ne & \mbox{\scriptsize I  } & 3  & 0  \\
         & \mbox{\scriptsize II}  & 68 & 232 (49) \\
         & \mbox{\scriptsize III} & 4  & 0  (0) \\
         & \mbox{\scriptsize IV}  & 1  & -- \\
\hline
\end{tabular}
\end{table}