I learned a new technique for night photography. If you expose with a fixed aperture at ISO 6400 then change the ISO to 100 at the same aperture just convey the number of seconds at 6400 to minutes at 100, i.e. 5 seconds at ISO 6400 = 5 minutes at ISO 100. This was a 7 minute exposure. The fine line is a jet passing through the image. More information, including this technique, can be found at the B & H YouTube channel.