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.
In the morning, civil twilight begins when the Sun is 6 degrees below the horizon and ends at sunrise. In the evening, it begins at sunset and ends when the Sun reaches 6 degrees below the horizon.
Astronomical twilight occurs when the sun is between 12 degrees and 18 degrees below the horizon. Night is classified when the sun is 18 degrees or farther below the horizon.
Astronomers recognize three different stages of twilight: civil twilight, nautical twilight and astronomical twilight. All three stages happen twice in a 24-hour period, between day and night and then repeating in reverse order between night and day.
Civil Twilight:
Begins in the morning, or ends in the evening, when the geometric center of the sun is 6 degrees below the horizon. Therefore morning civil twilight begins when the geometric center of the sun is 6 degrees below the horizon, and ends at sunrise.
Astronomical dawn begins when the Sun is 18 degrees below the horizon in the morning. Astronomical twilight follows instantly until the Sun is 12 degrees below the horizon.
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.
One word substitute is Dusk.
The word twilight was on a list of “words with atmosphere” that I sent her. Though these words were meant to be used in combination with something else, the word twilight stood out to both of us. We decided to try it out, and, after a little adjustment time, it started to work for both of us.
Lawmakers have enshrined the concept of civil twilight. Such statutes typically use a fixed period after sunset or before sunrise (most commonly 20–30 minutes), rather than how many degrees the Sun is below the horizon.
Astronomical twilight is the darkest of the three types of twilight. Together, astronomical, nautical and civil twilight describe the time between sunset and full dark, and between full dark and sunrise.
When does the golden hour occur? The golden hour occurs twice during the day: In the morning, it begins when the Sun is at -4º of elevation and it ends when the Sun is at 6º above the horizon. It matches the end of the civil twilight, just after the blue hour.
The last hour before sunset and the first hour after sunrise are coveted by professional photographers. Referred to as “the golden hour” or “magic hour,” these times provide the perfect light to capture stunning photos.
About 20 to 30 minutes before sunrise, if atmospheric conditions are right, the sky at the horizon to the east can develop a strong orange cast. On rare occasions, this light can be so strong it overpowers the blue light from the sky directly overhead, putting a diffuse warm glow over the landscape.
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.
the last years of someone's life: Old people often rely on pets for comfort and companionship in their twilight years.
In everyday language, the term dusk is commonly used as another word for evening twilight—the period from sunset until nighttime.
What are the definitions of dawn, dusk and twilight? Dawn is the time of morning when the Sun is 6° below the horizon. Respectively, dusk occurs when the Sun is 6° below the horizon in the evening.
While it's common to confuse twilight with dusk and dawn, they are different events. Dusk and dawn occur when the Sun's center is at the exact point below the horizon; twilight occurs between these points.
While first light is the first that appears, sunrise occurs when the sun makes its appearance. Twilight is that time when the atmosphere receives light from the sun, making it illuminated even before the sun actually rises or after the sets.
The blue hour generally lasts the 20 to 30 minutes just after sunset and just before sunrise. For example, if the sun sets at 5 p.m., the blue hour would last from approximately 5:10 p.m. to 5:30 p.m.. If the sun rises at 5 a.m., the blue hour lasts from about 4:30 a.m. to 4:50 a.m.