Panoramic London cityscape at twilight with views over the City of London. The Shard lit up though still under construction can be seen in the far right of the image, with familiar buildings the Gherkin (St Mary Axe), Tower 42 and the Heron Tower in the City of London to the left. The image is available for licence at ultra high resolution.
Nautical twilight is the part of twilight where the horizon becomes indistinct as the sun has dropped 12 degrees below the horizon line. At this point of the evening, sailors can no longer use the horizon to navigate by.