Well after sunset last evening, this crazy cloud layer remained brightly illuminated in the northern sky. Slowly the brightest illumination, which indicated the position of the sun below the horizon, moved from left (north-west) to right (north) and then slowly faded well after midnight.
At this time of year, the sun is never more than 18 degrees below the horizon, known as astronomical twilight. The period of time this cloud layer was illuminated was not long after sunset, so as the sun’s position, relative to the horizon, moved towards the north it was also dipping further below the horizon towards its lowest point, hence the gradual fade.
Summer Solstice is only a few days away. Since last December the sunset has moved progressively north along the Purcell skyline. In a few days, it shall begin to slide south again.