\begin{table}%t1
%\centering
\par
\caption{\label{tab_examples}Examples for parameters of an optimum timing in an OTF map covering 30 points in each line. All values are given for a spectral resolution of 1~MHz, corresponding to a typical fluctuation bandwidth of 1.5~MHz.}
\small \begin{tabular}{lrrrrrr}
\hline\hline\noalign{\smallskip}
observation & $t\sub{A}$ & $\alpha$ & $N$ & $t\sub{s}$ & $\sigma/\sigma(t\sub{tot})$ & $\sigma^2\sub{drift}/\sigma^2\sub{radio}$ \\
& [s] & & & [s] \\
 \hline
\multicolumn{7}{l}{Ground-based telescope: $t_{s,{\rm min}}=1$~s, 
$t\sub{d,1}+t\sub{d,2}=20$~s, $t\sub{turn}=8$~s}\\
%\hline
spectroscopic & 80 & 2.5 & 180 & 2 & 1.17 & 0.07 \\
total-power & 8 & 1.5 & 60 & 1 & 1.70 & 0.70 \\
%\hline
\multicolumn{7}{l}{HIFI at Herschel: $t_{s,{\min}}=1$~s, 
$t\sub{d,1}+t\sub{d,2}=80$~s, $t\sub{turn}=20$~s}\\
%\hline
spectroscopic & 150 & 2.5 & 180 & 4 & 1.23 & 0.10 \\
total-power & 10 & 1.5 & 150 & 1 & 2.13 & 1.03 \\
\hline
\end{tabular}
\end{table}