\begin{table}%t4
\caption{The DI dust cloud ``mass spectrometer'': Apex distance, radiation pressure
  factor $\beta$ and initial velocity as determined from the DI dust ejecta 
  envelope.\label{ejecta_cloud}}
%\centering
\par
\begin{tabular}{lcccc}
\hline\hline
Date/time        & Time after & Apex distance & $\beta$ & Velocity \\
(UT)             & impact (h) & (km)          &         & (m~s$^{-1}$)    \\
\hline
05-07-2005/02:45 & 20.9            & 14~100         & 1.9     & 370 \\
06-07-2005/00:00 & 32.0            & 19~400         & 0.65    & 260 \\
07-07-2005/00:00 & 66.1            & 22~900         & 0.3     & 190 \\
07-07-2005/23:00 & 89.2            & 25~000         & 0.2     & 160 \\
\hline
\end{tabular}
\end{table}