\begin{table}%t1
\caption{\label{tab:calibrators}Calibrator star information.}
\small%\centerline
 {
\begin{tabular}{lccccc}
  \hline\hline\noalign{\smallskip}
  Star                & $V$  & $K$  & Spectral & $d_{{\rm UD}}$\\
                      &      &      & type     & [mas]           \\
  \hline\noalign{\smallskip}
  \object{HD~108570} & 6.14 & 4.12 & K1III    & $0.72 \pm 0.05$~$^{(a)}$\\
  \object{HD~101328} & 7.44 & 3.75 & K4III    & $1.00 \pm 0.01$~$^{(b)}$\\
  \object{HD~104479} & 4.75 & 3.92 & K0III    & $0.76 \pm 0.01$~$^{(a)}$\\
  \object{HD~106248} & 6.35 & 3.73 & K2III    & $0.94 \pm 0.01$~$^{(a)}$\\
  \object{HD~111123} & 1.30 & 1.98 & B0.5IV   & $0.84 \pm 0.06$~$^{(a)}$\\
  \object{HD~121384} & 6.01 & 4.00 & G8V      & $0.76 \pm 0.05$~$^{(a)}$\\
  \object{HD~135452} & 6.88 & 3.43 & K3III    & $1.13 \pm 0.02$~$^{(a)}$\\
  \object{HD~145921} & 6.15 & 3.62 & K2III    & $0.96 \pm 0.01$~$^{(b)}$\\
  \object{HD~152534} & 6.77 & 4.54 & G8III    & $0.60 \pm 0.04$~$^{(a)}$\\
  \object{HD~170499} & 7.76 & 3.05 & K4III    & $1.24 \pm 0.02$~$^{(b)}$\\
  \object{HD~174631} & 6.11 & 2.94 & K1III    & $1.25 \pm 0.02$~$^{(b)}$\\
  \object{HD~177756} & 3.43 & 3.56 & B9V      & $0.53 \pm 0.04$~$^{(a)}$\\
  \object{HD~181110} & 7.30 & 3.71 & K3III    & $0.95 \pm 0.01$~$^{(b)}$\\
  \object{HD~183925} & 6.75 & 2.92 & K5III    & $1.44 \pm 0.02$~$^{(a)}$\\
  \hline
\end{tabular}}
\medskip
Notes. The $V$-band magnitudes were taken from SIMBAD and the \mbox{$K$-band} magnitudes from the 2MASS point source catalog.\\
References. $^{(a)}$ UD diameter computed with ASPRO.  $^{(b)}$ UD diameter determined with the ESO CalVin tool.
\end{table}