7 almucantar observations at 391.4 ± 5 nm (February 27, 2020): observations (in purple) and predictions for the model that best fits the data (Black stars ★). The model is a linear combination of ground and sky (including albedo) for a 11% polarised sky emission in a direction defined by an azimuth of 50° and −20° elevation (see text for details). The dashed vertical black line indicates the direction of Skibotn. The picture of the sky at 557.7 nm is shown in Appendix A. The emissions at 391.4 nm (purple) are considered to be similar.