\begin{table}%t2 \caption{\label{Tab_Photometry}Photometry of comet 133P/Elst-Pizarro.} %\centering \par \begin{tabular}{crrcccccc} \hline\hline\noalign{\smallskip} Date & \multicolumn{1}{c}{Phase} & \multicolumn{1}{c}{$r$\tablefootmark{(1)}} & \multicolumn{1}{c}{$\Delta$\tablefootmark{(2)}} & \multicolumn{3}{c}{$H_R$ $(\alpha)$ (mag)} & \multicolumn{2}{c}{$H_V$ $(\alpha)$ (mag)} \\ (yyyy mm dd) & \multicolumn{1}{c}{(\degr)} & \multicolumn{1}{c}{(AU)} & \multicolumn{1}{c}{(AU)} & acq.\tablefootmark{(3)} & aver. pol.\tablefootmark{(4)} & photom.\tablefootmark{(5)} & aver. pol.\tablefootmark{(4)} & photom.\tablefootmark{(5)} \\ \hline 2007 05 22 & 19.69 & 2.6467 & 2.0129 & 16.69 & 16.76 &16.53 & 17.26 & 16.82 \\ 2007 07 13 & 3.33 & 2.6424 & 1.6329 & & 15.76 &15.62 & 16.11 & 15.94 \\ 2007 07 17 & 1.66 & 2.6429 & 1.6282 & 15.57 & 15.75 &15.53 & 16.04 & 15.88 \\ 2007 08 01 & 4.95 & 2.6455 & 1.6466 & 15.68 & 15.86 &15.65 & 16.22 & 16.13 \\ 2007 08 05 & 6.68 & 2.6465 & 1.6619 & 15.91 & 15.69 &15.92 & 16.26 & 16.40 \\ 2007 08 09 & 8.20 & 2.6475 & 1.2794 & 15.95 & 15.82 &15.91 & 16.27 & 16.35 \\ 2007 08 30 & 15.32 & 2.6548 & 1.8342 &(16.19)& (16.34) &(16.51)&(16.33)&(16.82)\\ 2007 09 19 & 19.61 & 2.6646 & 2.0521 & 16.46 & 16.25 &16.36 & 17.00 & 16.94 \\ 2007 09 24 & 20.29 & 2.6674 & 2.1130 & 16.42 & &16.74 & 16.63 & 17.22 \\ \hline & 0.00 & & &\multicolumn{3}{c}{$15.50 \pm 0.05$}&\multicolumn{2}{c}{$15.88 \pm 0.07$} \\ \hline \end{tabular} \tablefoot{\tablefoottext{1}{Helio-centric distance to the object.} \tablefoottext{2}{Geo-centric distance to the object.} \tablefoottext{3}{Magnitude measured in the acquisition images.} \tablefoottext{4}{Magnitude measured in the averaged polarimetric frames.} \tablefoottext{5}{Magnitude measured in the frames obtained with no polarimetric optics in.} The last row refers to the brighntess at phase-angle 0\degr\ extrapolated with a linear best-fit. Blanks refer to frames where the image of \centotrentatre\ was contaminated by background objects. Values given in parenthesis should be considered as lower limits because obtained during a cloudy night.} \end{table}