\begin{table}%t2
\caption{\label{table:2}Astrometry of individual CCD frames of WFI mosaics.}
%\centering
\par
\begin{tabular}{c c c c c}
\hline\hline \noalign{\smallskip}
Sky    & \multicolumn{2}{c}{Mean errors}                                 & Frames          &  No. UCAC2      \\
path   & $\sigma(\Delta$$\alpha$cos$\delta)$  & $\sigma(\Delta$$\delta)$ & per year        &  stars/frame    \\
 year  &      mas                             &     mas                  &                 &                 \\
\hline
2008   &       59                             &      59                  &       112       &          105    \\
2009   &       58                             &      56                  &       112       &           79    \\
2010   &       58                             &      56                  &       128       &          164    \\
2011   &       61                             &      59                  &       160       &          153    \\
2012   &       63                             &      62                  &       168       &          125    \\
2013   &       63                             &      62                  &       168       &          107    \\
2014   &       62                             &      62                  &       184       &          105    \\
2015   &       58                             &      57                  &       168       &          132    \\
\hline
\end{tabular}
\tablefoot {Mean errors come from standard deviations of (O$-$C) residuals from individual (RA,~Dec) solutions with the UCAC2~catalog. The six constants polynomial model was used to relate ($x, y$) measurements with ($X, Y$) tangent plane coordinates. The ($x, y$) centers were pre-corrected by the FDPs. See details in Sect.~4.2.}
\end{table}