\begin{table}%t1
\caption{Summary of observing nights at the OSN. The mean accuracy of each dataset is also provided (see text for details).}\label{table:nights}
%\centering
\small
\begin{tabular}{cccccc} 
\hline
\hline
Dates & Observing & \multicolumn{4}{c}{Accuracy (mmag)}\\
      &      nights &   $u$  & $v$ & $b$ & $y$ \\
\hline
20--29 May 2002 & 10    &10  &6  & 6 & 7   \\
8--14 Jan. 2003 & 4      &9   & 4 & 3 & 4   \\
1--13 Jul. 2003 & 9     &8   & 4 & 4 & 6   \\
30 Jan.--8 Feb. 2004 &4 &10  & 5 & 5 & 6   \\
13--24 Jul. 2005 & 6   &10  & 5 & 5 & 5   \\
16--30 Jan. 2006 & 5   &7   & 4 & 4 & 5   \\
\hline
\end{tabular}
\end{table}