Blue Hour Gallery
Let's get the definition out of the way first ..... the blue hour is a period of twilight in the morning and evening during the civil and nautical twilight phases, when the sun is at a significant depth below the horizon and when the residual, indirect sunlight takes on a predominantly blue shade.
Or … it’s when the sky looks a surreal and often stunning shade of blue.
Blue hour skies work well for images, particularly ones in an urban setting.