Photographers talk about "golden hour" as if it were a fixed 60 minutes. It is not. Its length depends on your latitude and the season: near the equator it can be twenty minutes; in Iceland in June it can last most of the night. Lightpath's Light timeline exists so you never have to guess.
The timeline is one 24-hour strip for the selected day and location. The background bands are the sky states, computed from the sun's altitude:
| Band | Sun altitude | What it looks like |
|---|---|---|
| Daylight | above +6° | Full sun, hard shadows |
| Golden hour | +6° down to sunset (−0.8°) | Warm, long shadows, low contrast |
| Blue hour (civil twilight) | sunset to −6° | Deep even blue, city lights glowing |
| Nautical twilight | −6° to −12° | Horizon still visible, first bright stars |
| Astronomical twilight | −12° to −18° | Sky nearly dark, faint stars appearing |
| Full dark | below −18° | Night |
Sunset is taken as −0.8°, not 0°, because atmospheric refraction lifts the sun's disc by about that much when it sits on the horizon. These are the exact thresholds the app uses.
The solid line is the sun's altitude through the day; the dotted line is the moon's. The lighter shaded region low on the strip marks when the Milky Way core is above the horizon. The blue tick near the bottom is the core window — the hours when the core is up and the sky is dark.
Civil, nautical and astronomical twilight are not photographer's slang; they are formal definitions used by the U.S. Naval Observatory and by every almanac. Civil twilight ends when the sun's centre is 6° below the horizon, nautical at 12°, astronomical at 18°. For you, they map neatly onto three different kinds of photograph: the blue-hour cityscape (civil), the twilight seascape with a visible horizon line (nautical), and the point after which the Milky Way is worth shooting (astronomical ends).
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