\begin{table}%t1
\par
 %\centering
\par
 \caption{\label{t1}\dd ~and photometric reference stars.}
  \begin{tabular}{@{}ccccc@{}}
 \hline\hline
  Star  & RA      & Dec     &  USNO A2  \\
        & (J2000.0) & (J2000.0) &  $R$ mag    \\
 \hline
 Optical counterpart to\\
 SAX J2103.5+4545  & 21\hr 03\mm35~\fsec7 & +45\deg 45\arcm 04\farcs0 & 14.4  \\
 Star 1 & 21\hr 03\mm 20~\fsec15 & +45\deg 45\arcm 14\farcs6 & 12.1  \\
 Star 2 & 21\hr 03\mm 21\fsec99 & +45\deg 44\arcm 55\farcs5 & 13.8  \\
 Star 3 & 21\hr 03\mm 40~\fsec32 & +45\deg 46\arcm 22\farcs6 & 13.0  \\
 \hline
 \end{tabular}
 \end{table}