\begin{table}%t2 \caption{\label{tabres2}Filament contrasts for which the correlation is equal to zero.} \small%%\centerline { \begin{tabular}{ccc} \hline \hline Contrast & Fit & Literature \\ \hline $C_{\rm Ca}$ & 0.20 & 0.70 \\ $C_{\rm H\alpha}$ & 0.13 & 0.35 \\ $C_{\rm fil}$ & 0.30 & 0.20 \\ \hline $C_{\rm fil}$(corr = 0) & 1.16 & 3.08 \\ $C_{\rm fil}$(corr = 0)/$C_{\rm fil}$ & 3.9 & 15.4 \\ \hline \end{tabular}} \medskip Note 2. Given the fitted contrasts for the three types of structures or those found in the literature, a filament contrast for which the correlation is equal to zero is given, in absolute value and relative to the solar value (see Sect.~4 for details). \end{table}