\begin{table}%t1
  \caption{\label{tab:observations}Data used for this analysis. Spectra
    were taken with different high-resolution spectrographs.
    Detection of differential rotation requires higher resolution in
    slower rotators. The minimum rotation velocities required for
    determining the rotation law are given in Col.~4. From the
    147~spectra from which differential rotation could be determined, 28
    stars show signatures of differential rotation.} 
  %\centering
\par
  \begin{tabular}{crcccc}
    \hline
    \hline
        Instrument & Resolving power $\lambda/\Delta\lambda$ & Wavelength range [\AA]& min. $v~\sin{i}$ [km~s$^{-1}$] & Total \# of stars & \# of differential rotators\\
      \hline
      CES & 220~000 & 40 & 12 & 32 & 14\\
    FEROS & 48~000 & 6000 & 45 & 23 & 3\\
    FOCES & 40~000 & 6000 & 45 & 81 & 7\\
    FLAMES/UVES  & 47~000 & 2000 & 45 & 11 & 4\\
    \hline
    Total &&&& 147 & 28\\
        \hline
  \end{tabular}
\end{table}