\begin{table}%t1
%\centering
\par
\caption{The diffraction limit resolution for large solar telescopes using
values in the text ($\lambda = 630.2$~nm/ 1564.8~nm).\label{tab1}} % title of Table
\begin{tabular}{lllll }             % centered columns (1 columns)
\hline\hline                        % inserts double horizontal lines
 Telescope aperture &  Angular resolution & Spatial resolution & Number of diffraction & Full-Well-Depth Exposure Times at    \\
      $D_{\rm tel}$       &     $\theta_{\rm diff}$   &    $\Delta X$      & elements per arcsec   & Diffraction Limit with 1  pm {\it FWHM}     \\
    (m)        &   (arcsec)          &    (km)            &                       &  (s)                                 \\
\hline                        % inserts single horizontal line
 1                 & 0.16 / 0.39  & 115 / 285  &  \ \ 39 / 6    & 0.16 / 0.02 \\ % inserting body of the table
 2                 & 0.08 / 0.20  & \ 57 / 142  & \ 159 / 26   & 0.16 / 0.02  \\
 4                 & 0.04 / 0.10  & \ 29 / 71   & \ 639 / 103  & 0.16 / 0.02  \\
 6                 & 0.03 / 0.06  &\  19 / 48   & 1431 / 232  & 0.16 / 0.02 \\
\hline                                   %inserts single line
\end{tabular}
\end{table}