\begin{table}%t1
\caption{Log of observations of W601 and OI 201. Columns~1 and~2 give the UT~date and the Heliocentric Julian Date of the observations. Column~3 gives the total exposure time. Column~4 gives the peak signal to noise ratio per 1.8~km~s$^{-1}$ CCD~pixel (at $\sim$$708$~nm for W601, and at $\sim$$552$~nm for OI~201) in the spectra, and Col.~5 gives the signal to noise ratio per 1.8~km~s$^{-1}$ in the LSD Stokes $V$~profiles. Column~6 gives the longitudinal magnetic field.}
\label{tab:log}
%\centering
$$
\begin{tabular}{@{~}lcccc@{~~}r@{$\;\pm\;$}l@{~}}
\hline\hline
Date (d/m/y)       & HJD               & $t_{\rm exp}$ & $S/N$ & $S/N$     & \multicolumn{2}{c}{$B_{\ell}$} \\
UT Time & (2 450 000+) & (s)                  &        & (LSD)  & \multicolumn{2}{c}{(G)}           \\
\hline
\multicolumn{7}{c}{W601} \\
 10/08/06   6:09 & 3957.76004 & 3600 & 220 & 1910 &   --514 & 335 \\
 06/03/07 14:28 & 4166.10187 & 3600 & 180 & 1610 &   --313 & 427 \\
 06/03/07 15:35 & 4166.14879 & 3600 & 120 & 1010 & --1279 & 696 \\
 09/03/07 14:34 & 4169.10634 & 3600 & 190 & 1760 &  1391 & 394 \\
\\
\multicolumn{7}{c}{OI 201} \\
 04/03/07   9:49 & 4163.91136 &   960 & 150 & 1600 & --477 & 73 \\
 05/03/07   6:12 & 4164.76045 &   960 & 160 & 1820 & --543 & 65 \\
 06/03/07   6:47 & 4165.78497 &   960 & 160 & 1710 & --546 & 68 \\
 09/03/07   9:03 & 4168.87910 &   960 & 150 & 1490 & --471 & 76 \\
 \hline
\end{tabular}
$$
\end{table}