What time is blue hour today?
Blue hour is the part of twilight when the sun is just below the horizon, down to 6° below it: from sunset until civil dusk in the evening, and from civil dawn until sunrise in the morning. At mid-latitudes it lasts about 25 to 35 minutes.
Calculating for your location…
Next 7 days ·
Why the sky turns blue after sunset
Once the sun is below the horizon, the light you see is sunlight scattered through the upper atmosphere. On its long path it crosses the ozone layer, which absorbs orange and red light, and the sky is left a deep, even blue. It is still bright enough to light buildings and faces, but dim enough that street lights, windows and car lights hold their own instead of looking washed out.
How long blue hour lasts
Like golden hour, it is shortest near the equator and around the equinoxes, and much longer at high latitudes in summer. At the June solstice, anywhere north of about 49° never reaches full darkness, and near 60° the blue hour stretches to nearly two hours.
| Latitude | Mar 20 | Jun 21 | Dec 21 |
|---|---|---|---|
| Equator | 21 min | 23 min | 23 min |
| 20° N | 22 min | 25 min | 24 min |
| 30° N | 24 min | 27 min | 26 min |
| 40° N | 27 min | 33 min | 31 min |
| 50° N | 32 min | 45 min | 39 min |
| 60° N | 42 min | 107 min | 58 min |
Which part of it to use
The first minutes after sunset still carry warm colour low in the west. The deepest, most saturated blue usually comes in the second half, with the sun 4° to 6° below the horizon, when the sky and artificial lights are closest in brightness. After civil dusk the sky darkens quickly. Bring a tripod or find a steady surface: exposures of a few seconds are normal by the end.
Definitions vary
Some photographers define blue hour as the sun between 4° and 8° below the horizon. This site uses civil twilight, 0° to 6° below, because it is the standard astronomers publish and it matches when the light is practical for walking, filming and photographing without extra lights. Chinese photographers call this window 带密度 (“with density”), after how the sky records on film; there is a Chinese version of the countdown.