How golden hour is calculated

The sun's timing is pure astronomy — exact, repeatable, the same every year. Here's how Golden Hour turns your location into precise times, and how the shoot score reads the weather on top of them.

When is golden hour?

Golden hour isn't a fixed clock time. It's defined by how high the sun sits — its altitude above the horizon — so it shifts with your latitude and the season.

Golden hour — sun from about +6° down to roughly −4°. Low, warm, raking light with long shadows.
Blue hour — sun from about −4° to −6°. The sky glows cool and even after the sun has dropped away.
Sunrise & sunset — the moment the sun's upper edge meets the horizon: officially −0.833°, not 0°, because the atmosphere bends the light and the sun has width of its own.
Civil twilight — ends at −6°: still bright enough to get around without lights.

How this app calculates it

Golden Hour uses suncalc, an implementation of the algorithms in Jean Meeus's Astronomical Algorithms— the standard reference for this math. (NREL's Solar Position Algorithm, the SPA, is the rigorous gold standard, accurate to ±0.0003°; Meeus lands within about an arcminute, far finer than anyone needs to plan a shoot.)

From your latitude, longitude and the date, it tracks the sun's position through the day, finds the instants it crosses each altitude boundary above, and shows them in your location's local time — accurate to about a minute. It all runs in your browser: no account, no server, nothing stored.

The shoot score

Timing is exact. Whether the light is actually good is weather — so the shoot score blends the two. For the upcoming golden hour, it pulls the hourly forecast from Open-Meteo (cloud cover split into low, mid and high layers, plus visibility) and turns it into a 0–10 score:

Some high or mid cloud (~25–65%) — ideal. Those are the clouds that catch and scatter colour.
Heavy low cloud, fog or haze — flattens the light and blocks the sun at the horizon. Big penalty.
Dead-clear sky — reliable but rarely dramatic, so it lands around 6, not 10.

It's a forecast, not a guarantee. Weather moves, and the best skies often come from cloud that arrives — or clears — at the last minute. Treat the score as a nudge, not a promise.

Golden vs blue hour

Golden hour — sun +6° to −4°. Warm and directional, long shadows. Best for portraits and landscapes.
Blue hour — sun −4° to −6°. Cool, even, glowing. Best for cityscapes and lit windows against a deep-blue sky.