How to use it
- Choose a place and a date.
- Read the morning and evening golden hours and blue hours, in local time, with the direction of the sun.
- Use the week table to plan ahead.
5 practical uses
- Plan a portrait, a wedding or a landscape photo shoot.
- Time a film scene for warm or blue light.
- Know when to be at a viewpoint or a beach.
- Plan a drone flight for low light and long shadows.
- Schedule a property photo for the best light.
The maths behind it
The golden hour is the time the sun's altitude h lies between −0.833° (the horizon, with refraction) and 6°; the blue hour between −6° and −0.833°. Each boundary time is found from cos H = (sin h − sin φ sin δ) / (cos φ cos δ), where H is the hour angle, φ the latitude and δ the sun's declination for the day; the azimuth at each time comes from the same spherical triangle.
What the hours are
The golden hour is the time the sun is between the horizon and 6° above it: the light comes through a thick slice of air, loses its blue, and falls sideways, so faces glow and shadows are long and soft. It lasts about an hour in mid-latitudes, twenty minutes in the tropics and much longer near the poles. The blue hour is the civil twilight before sunrise and after sunset, the sun less than 6° below the horizon, when the sky is deep blue and the ground is lit evenly, good for cityscapes with the lights on.
Times are computed in the browser with the SunCalc library, which follows the astronomical almanac formulas to within a minute or so, and are shown in the local time of the place, including summer time, from its time zone. Sunrise and sunset are the moments the top edge of the sun meets a flat horizon, with the usual allowance for the bending of light in the air; a hill to the east delays your sunrise.