\begin{table}%t1
      \caption{\label{tab1}PM2000 data sources.}
      %\centering
\par
      \begin{tabular}{l l c}
      \hline\hline
      Source & Author & Epoch\\
      \hline
         AC2000.2     & Urban et~al. 1998 & $  \sim $1900    \\
         CdC2000      & Rapaport et~al. 2006        & $  \sim $1900   \\
         USNO-A2.0  & Monet et~al. 1998& $ \sim$1950     \\
         Yellow Sky (YS3.0)          & Unpublished & $ \sim$1978     \\
         M2000            & Rapaport et~al. 2006 & $ \sim $2000   \\
         \hline
       \end{tabular}\vspace*{-2mm}
   \end{table}