P_r of 67P dust in % (a) and the mean and 1σ error of the position angle of P_r with regard to the scattering plane (θ_r) as a functionof the wavelength (b) observed at α = 26°.4 on UT 2016 January 12. The black points in panel a were binned to have wavelength intervals of ~52 Å. The large error bars result from the remnants of the skylines that were not perfectly subtracted due to the limited slitwidth. The red solid and upper and lower dashed lines inpanel b indicate the weighted mean of θ_r (θ_{r, avg}) and its error(the standard deviation divided by the square of the number of the data points), respectively. The black line marks θ_r = 0°, the expected value when the dust is distributed randomly in the coma.