Blue hour

The blue hour (from French l'heure bleue;[1][a] pronounced [lœʁ blø]) is the period of twilight (in the morning or evening, around the nautical stage) when the Sun is at a significant depth below the horizon.

Rather, blue hour refers to the state of natural lighting that usually occurs around the nautical stage of the twilight period (at dawn or dusk).

[3] The blue hour is shorter in regions near the equator due to the sun rising and setting at steep angles.

In places closer to the poles, the illumination and twilight periods are longer as the sun rises and sets at shallower angles.

When photographing during blue hour it can be favourable to capture subjects that have artificial light sources, such as buildings, monuments, cityscapes, or bridges.