\begin{table}%t3
\caption{\label{tab3}Proper motion of the Crab pulsar.}
%\centerline
 {\small \begin{tabular}{l c c c}
\hline\hline\noalign{\smallskip}
Date & Knot & Star 1 & Star 2 \\
\hline  
94/08/14 & 0\myarcsec625(0.005)$^a$  & 5\myarcsec00 & 4\myarcsec94 \\
07/09/30 & 0\myarcsec635(0.012)  & 5\myarcsec22 & 5\myarcsec13 \\ 
\hline
\end{tabular}}
\medskip
$^a$ 3$\sigma$ pointing uncertainty. 
\end{table}