Twilight

Define:

Sunrise;

• Sunrise occurs when the upper limb of the sun (the first part visible) is on the visible horizon. 

Sunset;

• Sunset occurs when the upper limb of the sun (the last part visible) is just disappearing below the visible horizon.

Twilight;

• Twilight is the time when the Sun is below the horizon, but its rays illuminate the sky.
• It starts to become light before sunrise, and
• it stays light some time after sunset.
• This period of incomplete light, or darkness, is called twilight.

Civil Twilight

• is defined as the period when the centre of the Sun is between 0° and 6° below the horizon.

Morning Civil Twilight (MCT);

• MCT begins when the centre of the sun is 6° below the celestial horizon and ends at sunrise.

Evening Civil Twilight (ECT);

• ECT begins at sunset and ends when the centre of the sun is 6° below the celestial horizon.

Daylight;

• The period from the ‘beginning of morning twilight’ until the ‘end of evening twilight’.

Deriving or Calculating the MCT and ECT at a Given Location (UTC, NZST and NZDT)

DAYLIGHT TABLES

Daylight Zones and Tables

• New Zealand has been divided into eight Daylight Zones for the purpose of simplifying the planning of VFR flights within the country.
• The accompanying maps of New Zealand (Figure GEN 2.7-1 and Figure GEN 2.7-2) show the boundaries of each zone and Table GEN 2.7-1 gives the Coordinated Universal Time (UTC) of the beginning and end of daylight of each of those zones.