\begin{table}%t2[ht]             %% TABELLE 2
\caption{Expansion time scales from proper-motion measurements.
         The data are either from Palen \etal\ (\cite{Palen02}), optical
	 measurements, or from the compilation of Terzian (\cite{Ter97}),
	 radio measurements.  The angular radii, $\theta_{\rm rim}$, and their
	 expansion rate, $\dot{\theta}_{\rm rim}$, refer to the semi-minor axes.
	 The effective temperatures are spectroscopic values (M\'endez
	 \cite{MKH92}) or He~{\sc ii} Zanstra temperatures (Gorny, priv.\
	 comm.)
        }
\label{tab.proper}
%\centering
\par
\begin{tabular}{lrcrlll}
\noalign{\smallskip}
\hline\hline
\noalign{\smallskip}
Object   &  $T_{\rm eff}$\ \        & $\theta_{\rm rim}$ &
$\dot{\theta}_{\rm rim}\ \ \ \ \ $  &
$\hspace{3mm}\theta_{\rm rim}/\dot{\theta}_{\rm rim}$    & comment   & reference\\
	 &  [K]\ \ \ &   [mas] &[mas~yr$^{-1}$]& \hspace{6mm}  [yr]     &   \\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
 IC 2448         &  65~000  &  $4500  $   &  $2.25\pm0.6$ & $2000\pm\ \ 600 $  &  optical & Palen \etal\ (\cite{Palen02}) \\
 NGC 6578        &  67~000  &  $3360  $   &  $1.60\pm0.4$ & $2100\pm\ \ 600 $  &  optical & Palen \etal\ (\cite{Palen02}) \\
 NGC 6884        &  87~000  &  $2280  $   &  $1.14\pm0.3$ & $2000\pm\ \ 600 $  &  optical & Palen \etal\ (\cite{Palen02}) \\
\noalign{\smallskip}
 NGC 3242        &  75~000  &  $8800 $    &  $13.2\pm4.7$ & \hspace{1.4mm}
     $700\pm\ \ 300 $  &  radio & Hajian et~al. (\cite{HTB.95}) \\
 NGC 7662        & 100~000  &  $6200  $   &  $5.6\pm 5.0$ &  $1100\pm1000  $
&  radio & Hajian \& Terzian (\cite{HT.96})\\
 NGC 7027        & 200~000  &  $4000$     &  $4.7\pm1.0 $ & \hspace{1.4mm}
     $900\pm\ \ 200$ &  radio &  Hajian et~al. (\cite{HTB.93}), Masson (\cite{M.89}) \\
\noalign{\smallskip}
\hline
\end{tabular}
\end{table}