GNU Image Manipulation Program (GIMP) on GNU/Linux. (1) Levels to improve contrast, (2) slight saturation to enhance color, and (3) downscaling to 1,200 x 900 from the original at 2,576 x 1,932, which makes image noise less noticeable.

Twenty-two minutes after sunset and near the end of civil twilight I saw what looked like crepuscular rays. I see formations like these quite frequently, maybe a few times every month. To me, this phenomenon always seems more evident when the sun lies four to six degrees below the western horizon (it laid at five and a half degrees, in the above image). I also get the impression this happens more commonly during (or near) summer, when both humidity and aerosols tend to accumulate more heavily in the air.