It’s midnight, and I’m looking out the window down the street. The daylight has dimmed a little bit since the sun set at 11pm, but I can still clearly see every house, car, tree and leaf. We’re south of the Arctic Circle, so the sun technically sets here every day of the year, but that’s starting to feel like merely a technicality. Twilight can last for hours on either side of each day. We did some reading on the different types of twilight.
Civil Twilight occurs when the sun is 0-6 degrees below the horizon. The sun is gone, but you can still see well enough to be functional without artificial light. We are still fully in this zone after midnight these days. At the peak of summer, it will never get darker than this.
Nautical Twilight occurs when the sun is 6-12 degrees below the horizon. It’s now too dark to do things outside without a light, but you can still see the horizon (and therefore could navigate a ship). At this time of the year up here, it never gets darker than nautical twilight.
Astronomical Twilight occurs when the sun is 12-18 degrees below the horizon. It is pretty much functionally night to everyone except astronomers, who have to wait until after astronomical dusk (18 degrees) to see certain dim celestial objects.
In the winter here, the sun will only be barely above the horizon for a couple of hours a day, but there will be lengthy sunrise, sunset, and twilight periods.
Here’s a fun interactive sun graph for nearby Norman Wells.