\begin{table}%t2 
\caption{\label{tab2}Observational data for analyzed planetary nebulae. }
\small%\centering
\par
\begin{tabular}{
               l
               c @{\hspace{0.20cm}}
               c 
               c c l l c c c c c c c }
\hline
\hline\noalign{\smallskip}
  Name    & C$_{\rm opt}$ & O$^{++}$/O  & He$^{++}$/He & log~$n_{\rm e}$ & $\theta$ & $V_{\rm exp}$    & {\em{t}}$_{\rm kin}$ & log S$_{\rm H\beta}$ & log T$_{\rm Zan}$ & $M_{\rm gas}$ & $M_{\rm dust}$ \\
\noalign{\smallskip}
            &         &             &              & [cm$^{-3}$] & [\arcsec]& [km~s$^{-1}$]       & [year]    & [erg~cm$^{-2}$~s$^{-1}$~sr$^{-1}$] & [K]& [$M_\odot$] & [10$^{-3}~M_\odot$ ] \\
\hline\noalign{\smallskip}
  H 1-16    & 2.50    & 0.880       & 0.097        & 3.77        & 2.0      & 20$^{\rm R}$    & 2000$^r$ & $-$0.83            &      $-$           & 0.152     & 0.38       \\
  Hb 6      & 2.10    & 0.901       & 0.115        & 3.53        & 6.0      & 20$^{\rm RRA}$  &~~500$^s$ & $-$0.95            & $>$4.48         & {\em 0.2} & {\em 1.20} \\
  M 2-10    & 1.32    & 0.625       & $-$            & 3.10        & 4.2      &              &           & $-$2.00            &      $-$           & 0.208     & 1.00       \\
  H 1-50    & 0.68    & 0.959       & 0.093        & 3.69        & 1.4      & 23$^{\rm GZ,R}$ & 1300      & $-$0.62            &     4.77         & 0.148     & 0.18       \\
\vspace{0.1cm}
  H 1-20    & 2.31    & 0.896       & 0.013        & 3.57        & 3.3      & 18$^{\rm R}$    & 3800$^r$ & $-$1.30            &      $-$           & 0.223     & 0.68       \\
  Th 3-4    & 2.83    & 0.946       & 0.078        & 4.20        & 1.5      &              &           & $-$0.60            &      $-$           & 0.055     & 0.49       \\
  M 3-38    & 2.06    & 0.968       & 0.238        & 3.49        & 1.8      & 15$^{\rm R}$    & 2400$^r$ & $-$1.05            &      $-$           & 0.143     & 1.04       \\
  M 3-8     & 1.93    & 0.860       & $-$            & 3.73        & 3.2      &              &           & $-$1.48            &     4.50         & 0.095     & 0.53       \\
\vspace{0.1cm}
  H 1-40    & 2.52    & 0.939       & $-$            & 4.26        & 3.0      & 20$^{\rm GZ,R}$ & 1000      & $-$1.23            &      $-$           & 0.044     & 0.66       \\
  M 2-23    & 1.28    & 0.924       & $-$            & 4.00        & 1.0      & 14$^{\rm R}$    & 1500$^r$ & $-$0.15            &     4.73         & 0.108     & 0.02       \\
  He 2-260  & 0.76    & 0.012       & $-$            & 4.16        & 1.0      & 17$^{\rm G}$    & 3500      & $-$0.65            &     4.41         & {\em 0.2} & {\em 0.74} \\
  H 1-32    & 1.63    & 0.787       & $-$            & 3.74        & 1.0      & 11$^{\rm R}$    & 1900$^r$ & $-$1.37            &      $-$           & 0.012     & 0.07       \\
  H 1-35    & 1.33    & 0.525       & 0.002        & 4.26        & 1.5      & 10$^{\rm GZ}$   & 3100      & $-$0.26            &     4.65         & 0.103     & 0.20       \\
\hline
\end{tabular}
\tablefoot{The reported quantities are: logarithmic extinction at H$\beta$ (Col.~2); ionization  parameters O$^{++}$/(O$^{+}$+O$^{++}$) and He$^{++}$/(He$^{+}$+He$^{++}$)  (Cols.~3 and~4); electron density from [S~II] $\lambda$6717/6731 line  ratio (Col.~5); nebular diameter (Col.~6); nebular expansion velocity  (Col.~7); kinematic age (Col.~8); H$\beta$ surface brightness (Col.~9);  stellar temperature from Zanstra hydrogen method (Col.~10); mass of ionized  nebular gas (Col.~11) and mass of dust (Col.~12).
\\Kinematic ages {\em{t}}$_{\rm kin}$ are from \cite{Gesicki2000} and \cite{Gesicki2006} or calculated assuming distance 8.5~kpc ($r$) or from Shklovski method ($s$).}\vspace{-2mm}
\tablebib{$\rm RRA$ -- \cite{Robinson1982}, $\rm GZ $ -- \cite{Gesicki2000}, $\rm G $ -- \cite{Gesicki2006}, $\rm R $ -- \cite{Richer2008}.}
\end{table}