\begin{table}%t3
\caption{Parameters of the best fit model.} \label{resulttab}
%\centering
\par
\begin{tabular}{l l}
\hline  \hline
Parameter  &  Value\\
\hline 
Distance & 3.1 kpc (see Sect.~\ref{distance}) \\
{\it CSPN}: & \\
~~~~Luminosity & $L = 325$ $\pm$ $100~L_\odot$ \\
~~~~Effective temperature & $T_{\rm eff} = 121.5$ $\pm$ $6~{\rm kK}$ \\
~~~~Age from post-AGB & $t = 8300^{+1500}_{-500}$~years \\
~~~~White dwarf mass & $M = 0.605$ $\pm$ $0.02~M_\odot$ \\
{\it PN gas shell}: & \\
~~~~Average radius & angular 22\arcsec \\
~~~~& linear $r = 1.02$ $\times$ $10^{16}~{\rm m}$ \\
~~~~Thickness & $\Delta_r/r = 0.2$ \\
~~~~Filling factor & $\epsilon = 0.05$ (adopted)  \\
~~~~Electron density & $n_{\rm e} = 200$ $\pm$ $100~{\rm e}^-~{\rm cm}^{-3}$ \\
~~~~Abundances: & \\
~~~~~~Helium & [He] = $-$0.83 \\
~~~~~~Nitrogen & [N] = $-$4.00 \\
~~~~~~Oxygen & [O] = $-$3.40 \\
\hline 
\end{tabular}
\end{table}