\begin{table}%t2
\caption{Observational configurations employed in the four different observing 
runs.
\label{observations}}
%\centering
\par
\small
\begin{tabular}{@{}lllll@{}}
\hline\hline
  & Run 1 & Run 2 & Run 3 & Run 4 \\
\hline
  Dates               & 19--21 Jan. 1998  & 15--17 Mar. 1999 &18--19 Aug. 1999  & 25--27 Apr. 2001\\  
  Telescope           & CAHA 3.5 m       & WHT 4.2 m       & CAHA 3.5 m      & WHT 4.2 m\\
  Spectrograph        & CTS              & ISIS blue       & CTS             & ISIS blue\\
  Detector            & CCD TEK 12       & EEV12           &CCD TEK 12       & EEV12\\
  Dispersion          & 1.08 \AA/pixel   & 0.80 \AA/pixel  & 1.08 \AA/pixel  & 1.72 \AA/pixel \\
  Wavelength range    & 3570--5770 \AA   & 3700--5269 \AA  & 3570--5770 \AA  & 3700--6151 \AA \\
  Spectral resolution & 3.6 \AA\ (FWHM)   & 3.5 \AA         &  3.6 \AA        &  6.56   \AA \\
  Slit width          & 2.1 arcsec       & 2.0 arcsec      & 2.1 arcsec      & 2.0 arcsec \\
  Spatial scale       & 1.1 arcsec/pixel & 0.8 arcsec/pixel& 1.1 arc/pixel   &  0.8 arcsec/pixel \\  
\hline
\end{tabular}
\end{table}