Civil Twilight:
Under these conditions absent fog or other restrictions, the brightest stars and planets can be seen, the horizon and terrestrial objects can be discerned, and in many cases, artificial lighting is not needed..
The truth is that pilots who fly at night will navigate using instruments instead of what they can see outside.
This type of flying is conducted under instrument flight rules.
Some ground features may be visible, but visual cues aren't normally as reliable in the darkness as in the daytime..
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..
Civil twilight is the brightest of the 3 twilight phases.
The Sun is just below the horizon, so there is generally enough natural light to carry out most outdoor activities..
3 types of twilight
Astronomers recognize three different stages of twilight: civil, nautical and astronomical.
All three stages happen twice in a 24-hour period, between day and night and then repeating in reverse order between night and day..
There are three established and widely accepted subcategories of twilight: civil twilight (nearest the horizon), nautical twilight, and astronomical twilight (farthest from the horizon)..
Civil twilight is defined as when the geometric center of the Sun is between 6\xb0 below the horizon and the horizon itself.
Civil twilight is the period when enough natural light remains that artificial light in towns and cities is not needed..
To explain further, the National Weather Service defines evening civil twilight as the time that begins in the morning, or ends in the evening, when the geometric center of the sun is 6 degrees below the horizon..
Civil twilight is a scientific term, and we define it as “the period after sunset or before sunrise ending or beginning when the sun is about 6 degrees below the horizon and during which on clear days there is enough light for ordinary outdoor occupations.” Some sources claim that the word was coined by the Swiss .
The darkest of the twilights is astronomical; to an astronomer, it's not the same as night, but to the layperson it's close enough.
Nautical twilight is a deep dusk — dim bluish sky, bright planets visible.
In civil twilight, the sky is light all over though the sun is not visible..
— Civil twilight ends in the evening when the centre of the sun's disc is 6 degrees below the horizon and begins in the morning when the centre of the sun's disc is 6 degrees below the horizon.
Existing definition..
The darkest of the twilights is astronomical; to an astronomer, it's not the same as night, but to the layperson it's close enough.
Nautical twilight is a deep dusk — dim bluish sky, bright planets visible.
In civil twilight, the sky is light all over though the sun is not visible..
Here's the Navy's definition: "civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon." A good rule-of-thumb for calculating civil twilight is that it usually ends between 20-35 minutes after sunset..
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..
Civil twilight is a scientific term, and we define it as “the period after sunset or before sunrise ending or beginning when the sun is about 6 degrees below the horizon and during which on clear days there is enough light for ordinary outdoor occupations.” Some sources claim that the word was coined by the Swiss .
You can log night flying time whenever you are in the aircraft and civil twilight has ended
For Instance if you start a flight at 6 PM local, civil twilight ends at 7 PM local and you shut the engine down at 9 PM local, you can log two hours of night flying time
Can’t I Just Use Sunset & Sunrise Times? No
Each twilight phase is defined by the solar elevation angle, which is the position of the Sun in relation to the horizon
During civil twilight, the geometric center of the Sun's disk is at most 6 degrees below the horizon
In the morning, this twilight phase ends at sunrise; in the evening it begins at sunset
What Is “Civil Twilight?” According to the AIM and Pilot/Controller Glossary, “civil twilight” is defined as follows: ,“Civil twilight ends in the evening when the center of the sun’s disk is 6 degrees below the horizon and begins in the morning when the center of the sun’s disk is 6 degrees below the horizon
”Here's the Navy's definition: ,"civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon
" A good rule-of-thumb for calculating civil twilight is that it usually ends between 20-35 minutes after sunset
Atmospheric illumination by the Sun below the horizon
Atmospheric illumination by the Sun below the horizon
