\begin{table}%t1
%\centering
\par
\caption{\label{tab1}Optical observations of accreting white dwarfs used for
construction of power spectra.}
\par
\begin{tabular}{lcccccc}
\hline\hline \noalign{\smallskip}
Target & Instr.& Dates&Mag.&Time res., s& Exp., ks & Spin Period, s\\
\hline
XSS J00564+4548&RTT150&2005.10.19--23,26,28&14.9(V)&17-128&71.6&465\\
               &      &2005.12.05,06        &14.6(R)&      &    &   \\
IGR J00234+6141&RTT150&2005.09.10--11,12.01&16.7(R)&60-70&37.6&561\\
               &      &2005.12.10--11,2007.09.03&16.7(R)&   &   \\
DO Dra    & RTT150&2007.04.24,27,28 &14.7(R)& 1 &48& 529\\
          &       &2008.05.24--26,06.03&14.8($g'$)&1-8&39&\\
V1223 Sgr & SALT  &2008.05.13,2008.06.12   &$\sim$13.3(B)&0.1 & 2.9&745\\
IGR J15094-6649&SAAO, 1m&2008.04.26--29&14.6(V)&7-8&14.9&809\\
IGR J16500-3307&SAAO, 1m&2008.04.27-28,05.04&15.9(V)&8--10&18.4&598\tablefootmark{*}\\
               &SAAO, 0.76m&2008.08.03--05      &15.9(V)&  &\\
IGR J17195-4100&SAAO, 0.76m&2008.08.5--10&15.2(V)&8&32.3&1139\tablefootmark{*}\\
\hline
\end{tabular}
\tablefoot{
\tablefoottext{*}{-- Here we use the optical pulsation period, which also may be the beat frequency instead of the true spin frequency of the white dwarf.}}
\end{table}