The Earth
The Solar System & Time
Using Aeronautical Charts
Basics of Navigation
Distance, Speed & Time
Vertical Navigation
Fuel Planning
Practical Navigation Techniques
Radio Navigation
Practice Exam

Sunrise, Sunset & Twilight

Sunrise and Sunset

Official sunrise is when the ‘upper limb’ of the rising sun first appears on the horizon, and official sunset it when the ‘upper limb’ of the setting sun disappears below the horizon.

The ‘upper limb’ is the very edge of the sun.


Some light can still be seen before sunrise and after sunset. This time is known as twilight and it starts and ends when the centre of the sun is 6° below the horizon.

Morning civil twilight starts when the rising sun’s centre is 6° below the horizon and ends at sunrise.

Evening civil twilight starts at sunset and ends when the setting sun’s centre is 6° below the horizon.

In aviation, official night is said to start 30 minutes after sunset and end 30 minutes before sunrise.

However, poor visibility and/or cloud cover can obscure the light and cause daylight to finish earlier than the published time of night.

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