Knowing exactly when the light changes is the difference between catching a shot and missing it. This calculator computes sunrise, sunset, golden hour, and all three twilight stages for any location and date using the same NOAA solar position algorithm that powers professional almanacs.
The three twilight stages and what they mean for photographers
The sun moves through distinct light zones before sunrise and after sunset. Each has a practical meaning:
Golden hour (civil twilight period)
The sun is between about -6 and +6 degrees of the horizon. Light is warm, directional, and soft — the “magic hour” that portrait and landscape photographers plan entire shoots around. In practical terms this window can be as short as 20 minutes in the tropics and over an hour at high latitudes in summer.
Blue hour (civil to nautical twilight)
After sunset, as civil twilight ends and nautical twilight begins, the sky turns a deep saturated blue. Artificial lights in a city scene balance well against the sky at this stage, which is why architectural and urban photographers specifically target the blue hour rather than the earlier golden window.
Nautical twilight
The sun is between -6 and -12 degrees. Enough ambient light remains for navigation by sea horizon but it is no longer useful for most photography. Wide-angle milky-way shooters who are waiting for full dark spend this time setting up.
Astronomical twilight and true dark
Between -12 and -18 degrees, scattered sunlight still affects the sky faintly. Once the sun passes -18 degrees, astronomical twilight ends and the sky is genuinely dark — the only window for imaging faint deep-sky objects without sky-glow contamination from residual sunlight.
How it works
The sun’s position is found from the date’s Julian century, which gives the geometric mean longitude, the equation of time, and the solar declination. For a target sun altitude angle, the hour angle is:
cos(H) = ( sin(altitude) − sin(lat)·sin(declination) )
/ ( cos(lat)·cos(declination) )The hour angle H (in degrees) is converted to minutes and applied either side
of solar noon. Solar noon itself is 720 − 4·longitude − equationOfTime
minutes UTC, which is then shifted to your local clock. Each event uses a
different altitude angle: -0.833 degrees for sunrise and sunset (allowing for
refraction and the sun’s radius), -6 for civil, -12 for nautical, and -18 for
astronomical twilight.
Tips and notes
At high latitudes in summer the sun may never reach -18 degrees, so astronomical twilight never ends and the sky stays partly lit all night — the tool reports “No darkness” in that case. For landscape and portrait work, shoot during the golden hour window flagged around sunrise and sunset. For Milky Way and deep-sky imaging, wait until astronomical twilight ends. The offset you enter is your UTC offset including any daylight-saving adjustment — add one hour during summer time if your region observes it.