Notes. λ_p and W_eff = [∫T(λ)dλ][Max(T(λ))]⁻¹ are the pivot wavelength and the effective width of the filter, ϕ is the fraction of source counts in the aperture with radius r_extr, C_tot is the total count rate in the source aperture, $C_{\mathrm{bgd}}={\overline{C}}_{\mathrm{bgd}}\pm {\sigma }_{C_{\mathrm{bgd}}}$, ${\overline{C}}_{\mathrm{bgd}}$ and σ_Cbgd are the mean and standard deviation of background measurements. C_s is the net source count rate; its error is estimated as $[{({\sigma }_{C\mathrm{bgd}}^2+C_s{t}_{\exp }^{-1}{g}^{-1}]}^{1/2}$, where g is the gain, ⟨f_ν⟩ = C_s𝒫_ν/ϕ is the mean flux density; and 𝒫_ν is the count rate-to-flux conversion factor.