If you’re an astronomer it’s important to know exactly when the sky is going to be properly dark so you can go outside and see all of the stars and planets that are waiting for you. You don’t want to go out too early, but you also don’t want to wait too long because then it will be too late!
There are a few different factors that influence how long after sunset it gets dark. One of the biggest factors is how close you are to the equator because locations closer to the equator experience much less variation in darkness than places farther away. In some places near the equator, it can be completely dark just 20 or 30 minutes after sunset!
Another factor that influences how long after sunset it gets dark is the season. It takes longer to get dark in the winter than it does in the summer because the sun is lower in the sky during the winter. Depending on how far north you are, you can have periods of time in the summer when it never really gets dark at all. The city of Bellingham in Washington state, for example, has two weeks in June when astronomical twilight doesn’t end before the sun rises again!
The last big factor that influences how long after sunset it gets night is the type of twilight that is currently happening. There are several types of twilight, including civil twilight, nautical twilight and astronomical twilight. Civil twilight is the final stage of twilight and is when it starts to get dark enough to begin stargazing. During nautical twilight, it’s still light enough to navigate by sight and during astronomical twilight, it has reached its darkest point where the sun is 12 degrees below the horizon.