USA HISTORY

Detailed explanation-1: -In its most general sense, twilight is the period of time before sunrise and after sunset, in which the atmosphere is partially illuminated by the sun, being neither totally dark or completely lit. However there are three categories of twilight that are defined by how far the sun is below the horizon.

Detailed explanation-2: -Twilight is the period between sunset and dusk. During twilight there is still light in the sky. There are three types of twilight: civil, nautical and astronomical. Dusk is the point when the sun is at 18 degrees below the horizon and there is no longer any sunlight in the sky.

Detailed explanation-3: -Astronomical twilight begins about an hour to 1 1/2 hours after sunset for mid latitudes. So, as a rule of thumb, if you’d like to observe something in the night sky that isn’t particularly bright, you should wait about 90 minutes after sunset before you start observing.

Detailed explanation-4: -The morning twilight is often called dawn, while the evening twilight is also known as dusk. Astronomical terms & definitions.

Detailed explanation-5: -These stages also occur before sunrise, in the reverse order. Civil twilight starts at sunset and ends roughly 45 minutes later, when the sun’s center has plunged six degrees below the horizon-equal to 12 times its own width.