What is Nautical Twilight?
Nautical twilight is a period in the morning and evening when the sun is between six and 12 degrees below the horizon. Some visible light is present, but not enough to conduct detailed activities without the use of artificial light, and the horizon tends to be somewhat indistinct during this period. People refer to this time of day as “nautical twilight” to reference the fact that sailors often took navigational observations during this time, since the visibility was ideal. While many people think of twilight as a time roughly between when it is not totally dark and when it is clearly light outside, this period of the day is actually broken into several distinct categories. Civil twilight occurs when the sun is less than six degrees below the horizon, allowing people to see things clearly, although the sun is obviously on the way up or down. Next comes nautical twilight, followed by astronomical twilight between 12 and 18 degrees, and when the sun is more than 18 degrees below the hori
