\begin{table}%t2 \caption{\label{tabella2}Magnitudes of VLBL candidates from our observational campaign; the error associated to the $B$ and $R$~filters is 0.05~mag.} %\centering \small \begin{tabular}{cccccccccc} \hline\hline\noalign{\smallskip} Source & Julian date & $B$ mag & $R$ mag & $J$ mag & err & $H$ mag & err & $K$ mag & err \\ \hline \a & 2~453~387.5 & 18.15 & 17.11 & & & & & & \\ & 2~453~465.5 & 18.72 & 17.67 & 15.97 & 0.05& 15.18 & 0.07& 14.26 & 0.09\\ & 2~453~738.5 & 18.56 & 17.75 & & & & & & \\ & 2~453~796.5 & 18.44 & 17.43 & & & & & & \\ & 2~453~823.5 & 18.55 & 17.53 & & & & & & \\ \hline \b & 2~453~387.5 & 18.67 & 17.83 & & & & & & \\ & 2~453~437.5 & 17.31 & 16.56 & & & & & & \\ & 2~453~466.5 & 17.73 & 16.96 & 15.26 & 0.04& 14.44 & 0.06& 13.36 & 0.07\\ & 2~453~738.5 & 17.82 & 17.23 & & & & & & \\ & 2~453~796.5 & 18.43 & 17.60 & & & & & & \\ \hline \c & 2~453~387.5 & 19.71 & 18.64 & & & & & & \\ & 2~453~465.5 & 19.48 & 18.32 & 16.66 & 0.03& 15.75 & 0.05& 14.51 & 0.05\\ & 2~453~738.5 & 19.43 & 18.33 & & & & & & \\ & 2~453~822.5 & 19.59 & 18.40 & & & & & & \\ \hline \d & 2~453~387.5 & 19.57 & 18.21 & & & & & & \\ & 2~453~439.5 & 18.98 & 17.72 & & & & & & \\ & 2~453~466.5 & 19.38 & 18.06 & 16.41 & 0.07& 15.45 & 0.14& 14.55 & 0.16\\ & 2~453~738.5 & 18.52 & 17.26 & & & & & & \\ & 2~453~823.5 & 17.96 & 16.79 & & & & & & \\ & 2~453~823.5 & & 16.77 & & & & & & \\ \hline \e & 2~453~557.5 & & 17.08 & & & & & & \\ & 2~453~415.5 & 19.06 & 17.86 & & & & & & \\ & 2~453~796.5 & 18.66 & 17.51 & & & & & & \\ & 2~453~885.5 & 18.56 & 17.52 & & & & & & \\ \hline \f & 2~453~466.5 & 20.09 & & & & & & & \\ & 2~453~466.5 & 20.04 & 18.65 & 16.85 & 0.05& 16.06 & 0.08& 14.71 & 0.08\\ & 2~453~497.5 & 19.94 & 18.55:& & & & & & \\ & 2~453~796.5 & 21.06:& 19.40:& & & & & & \\ & 2~453~823.5 & & 19.35 & & & & & & \\ & 2~453~915.5 & 20.11 & 18.71 & & & & & & \\ \hline BZB~J1927+6117 & 2~453~498.5 & 17.72 & 17.22 & & & & & & \\ & 2~453~527.5 & 17.78 & 17.24 & 15.80 & 0.02& 14.95 & 0.03& 13.96 & 0.03\\ & 2~453~557.5 & 17.78 & 17.24 & & & & & & \\ & 2~453~565.5 & 17.79 & 17.24 & & & & & & \\ & 2~453~579.5 & 17.91 & 17.33 & & & & & & \\ & 2~453~643.5 & 17.86 & 17.32 & & & & & & \\ & 2~453~885.5 & 17.69 & 17.08 & & & & & & \\ & 2~453~915.5 & 17.80:& 17.26 & & & & & & \\ & 2~453~981.5 & 17.92 & 17.33 & & & & & & \\ & 2~453~982.5 & 17.95 & 17.34 & & & & & & \\ & 2454015.5 & 17.67:& 17.34 & & & & & & \\ & 2454051.5 & 18.00 & 17.39 & & & & & & \\ \hline \l & 2~453~527.5 & & 18.87 & 17.17:& 0.03& 15.58 & 0.03& & \\ & 2~453~738.5 & 20.03 & & & & & & & \\ & 2~453~915.5 & & 19.25 & & & & & & \\ & 2~453~981.5 & 20.51 & 19.30 & & & & & & \\ & 2~453~982.5 & 20.71 & 19.30 & & & & & & \\ \hline \end{tabular} \end{table}