\begin{table}%t2
\caption{\label{Tab_Observations} 
Determination of the mean longitudinal magnetic field of 17 RR~Lyrae
stars.  
}
%\centerline
$$
\begin{tabular}{llccccrcr@{~$\pm$~}lc}
\hline \hline\noalign{\smallskip}
\multicolumn{1}{l}{Object}       &
\multicolumn{1}{l}{Type}         &
\multicolumn{1}{c}{Date}         &
\multicolumn{1}{c}{Time (UT)~{\bf $^{(1)}$}}    &
\multicolumn{1}{c}{Exp~{\bf $^{(2)}$}}          &
\multicolumn{1}{c}{Slit}         &
\multicolumn{1}{c}{$\phi$~{\bf $^{(3)}$}}       &
\multicolumn{1}{c}{$\psi$~{\bf $^{(4)}$}}       &
\multicolumn{2}{c}{\Bz}          &
\multicolumn{1}{c}{({\it SNR})~{\bf $^{(5)}$}}          \\
\multicolumn{1}{c}{}             &
\multicolumn{1}{c}{}             &
\multicolumn{1}{c}{(yyyy mm dd)} &
\multicolumn{1}{c}{(hh:mm)}      &
\multicolumn{1}{c}{(sec)}        &
\multicolumn{1}{c}{width}        &
\multicolumn{1}{c}{($\pm$0.02)}             &
\multicolumn{1}{c}{}             &
\multicolumn{2}{c}{(G)}          &
\multicolumn{1}{c}{} \\
\hline
       &        &            &       &      &           &     & & 
\multicolumn{2}{c}{} & \\
WZ Hya & RRab   & 2008 11 12 & 08:32 & 1920 & 0.5\arcsec&0.99 &--& 32 & 21& 2620 \\ 
V Ind  & RRab   & 2008 11 13 & 03:03 & 2400 & 1.0\arcsec&0.89 &--&  $-$57& 28& 2820 \\ 
U Lep  & RRab   & 2008 11 11 & 05:06 & 2340 & 0.5\arcsec&0.23 &--&  $-$15& 19& 2930 \\ 
RU Scl & RRab   & 2008 11 11 & 02:26 & 3900 & 0.5\arcsec&0.63 &--&      6& 14& 2865 \\ 
CS Eri & RRc    & 2008 11 12 & 02:36 & 960  & 0.5\arcsec&0.41 &--&      3& 19& 3025 \\ 
       &        & 2008 11 13 & 06:10 & 360  & 0.5\arcsec&0.10 &--&      5& 22& 2900 \\
MT Tel & RRc    & 2008 11 11 & 00:10 & 1800 & 0.5\arcsec&0.07 &--&  $-$44& 29& 3370 \\ 
RV Cap & RRab-BL& 2008 11 13 & 01:56 & 4000 & 1.0\arcsec&0.17& 0.4$\pm$0.1 &   $-$4& 31& 2640 \\ 
RX Cet & RRab-BL& 2008 11 12 & 03:41 & 4560 & 0.5\arcsec&0.92 & * &     45& 21& 1970 \\ 
RV Cet & RRab-BL& 2008 11 11 & 06:03 & 2880 & 0.5\arcsec&0.31 & 0.0$\pm$0.2 &   $-$6& 15& 2535 \\ 
RX Col & RRab-BL& 2008 11 11 & 07:24 & 4800 & 1.0\arcsec&0.19 & 0.5$\pm$0.2 & $-$99& 45& 1480 \\ 
RY Col & RRab-BL& 2008 11 11 & 03:53 & 4700 & 1.0\arcsec&0.28 & 0.2$\pm$0.1 &     18& 23& 3020 \\ 
VW Dor & RRab-BL& 2008 11 12 & 07:35 & 3360 & 1.0\arcsec&0.27 &  * &  $-$38& 28& 2270 \\ 
SS For & RRab-BL& 2008 11 11 & 01:12 & 3440 & 0.5\arcsec&0.61 & 0.43$\pm$0.10 &   2& 19& 2930 \\ 
       &        & 2008 11 12 & 06:41 & 1440 & 0.5\arcsec&0.09 & 0.47$\pm$0.10 &   $-$5& 20& 2710 \\
       &        & 2008 11 13 & 04:14 & 1440 & 0.5\arcsec&0.90 & 0.49$\pm$0.10 &  $-$16& 30& 1875 \\
RX For & RRab-BL& 2008 11 13 & 05:17 & 4413 & 1.0\arcsec&0.64 & 0.8$\pm$0.4 &     15& 34& 1855 \\ 
SZ Hya & RRab-BL& 2008 11 11 & 08:40 & 1920 & 0.5\arcsec&0.16 &  * &  21& 25& 2160 \\ 
X Ret  &RRab-BL & 2008 11 12 & 05:16 & 4800 & 1.0\arcsec&0.76 & 0.9$\pm$0.2 &   $-$4& 29& 2250 \\ 
BV Aqr & RRc-BL & 2008 11 12 & 01:46 & 3360 & 1.0\arcsec&0.44 & * &      6& 27& 3620 \\ 
HD 94660& Magnetic Ap & 2008 11 12 & 09:01 &   56 & 0.5\arcsec&     & &$-$1831& 15& 3280 \\
       &        & 2008 11 12 & 09:08 &   28 & 1.0\arcsec&     & &$-$1872& 25 &3071 \\
\hline
\end{tabular}
$$
$^{(1)}$ The epoch of the observations refers to the middle of the eight
exposures, and  $^{(2)}$ the exposure time refers to the sum of eight exposures.\\
$^{(3)}$ $\phi$: pulsation phase;  $^{(4)}$ $\psi$: Blazhko phase. The symbol
``--'' is used for non-Blazhko stars.  The symbol ``*''
is used for Blazhko stars for which the Blazhko phase could not be obtained with an
error smaller than 0.5. \\
 $^{(5)}$ The signal-to-noise ratio (SNR) is calculated per \AA, in the wavelength
interval 4475--4525~\AA.
\end{table}