All of us on the northern hemisphere are experiencing it: short winter days. Although the lack of light can be depressing from time to time, the late sunsets make it a lot more comfortable to witness twilight in the morning.
A photo I took of the twilight behind the Øresund Bridge bridge between Denmark and Sweden.
Today I learned that twilight, the time between light at the horizon and actual sun coming over the horizon (sunrise), has various definitions.
There is the civil twilight as we, the land lovers, know it. This is when the sun's geometrical center is about 6 degrees below the horizon. Then there is the nautical twilight. In this case the sun is 12 degrees below the horizon. And then finally there is the astronomical twilight with the sun about 18 degrees below the horizon.
I never knew there were different definitions of twilight used in the world, so I was happy to learn about them.
The nautical twilight is actually the period during which you can already see things, but not yet clearly navigate the seas using the horizon. The astronomical twilight relates to the ability to observe the universe. E.g. to see stars etc.
All of the above also applies to the end of the day during sundown.
When did you last observe twilight?