\begin{table}%t2
\caption {\label{ampl}Amplitudes and phases of the leastsquares fit to the merged~U, 
B and V+ light curves of HD~180~642.}
%\centerline
 {\begin{tabular} {l cc cc cc}
\hline
 \hline
Freq.& \multicolumn{2}{c}{U \& $u$} & \multicolumn{2}{c}{B \& $v$} & \multicolumn{2}{c}{V \& $y$ \& $V$}  \\ \hline
  (\cd)  & Ampl & Phase & Ampl & Phase & Ampl & Phase    \\ 
    &(mmag)& (rad)&(mmag)& (rad)&(mmag)& (rad) \\ \hline
$f_1 = 5.48694$ & 82.7(7) & 2.884(9) & 48.1(5) & 2.88(1) & 38.1(5)   &  2.86(1) \\
$2f_1 = 10.97388$ & 8.2(7) & 1.48(9) & 6.6(5) & 1.52(8) & 5.3(5) & 1.4(1)   \\
$3f_1 = 16.46082$ & 4.3(7) & 2.0(2) & 4.3(5) & 2.1(1) & 3.6(5) & 1.9(2)   \\
$f_2^p = 0.30818$ & 4.9(7) & 0.9(2) & 3.1(5) & 1.1(2) & 1.6(5) & 0.9(4)  \\
$f_3^p = 7.36673$ & 4.5(7) & 5.4(2) & 3.1(5) & 5.4(2)  & 2.2(5)  &  5.7(3)  \\
\noalign{\smallskip}
\hline
Var. Red. & \multicolumn{2}{c}{96.6\%}  & \multicolumn{2}{c}{95.3\%}& \multicolumn{2}{c}{81.8\%}\\
Residual rms (mmag) & \multicolumn{2}{c}{11.4}  & \multicolumn{2}{c}{7.9}& \multicolumn{2}{c}{12.9} \\
\noalign{\smallskip}
\hline
\end{tabular}}
\par
\smallskip
 {Errors in units of the last digit are given in brackets. The amplitude is expressed in millimag, and the phase is given in radians. The adopted reference epoch for $\phi=0.0$ corresponds to HJD~2~447~963.2564. For each combined dataset the total variance reduction of the quintu-periodic model and the root mean square (rms) of the residuals is reported.} 
\end{table}