The Golden Hour and the Blue Hour Are Angles, Not Hours

The four thresholds the tool actually uses

Four numbers define the whole page. Above +6° of solar elevation is full daylight. From +6° down to −4° is golden hour. From −4° down to −6° is blue hour. Below −6° is night. Sunrise and sunset are a separate threshold at −0.833°, and separate is the right word — if it were treated as a phase edge it would cut the golden band in two, which is precisely what it must not do, because the sun crossing the horizon is an event inside the golden hour and not its boundary.

That −0.833° is not a fudge. The US Naval Observatory defines sunrise and sunset as the moment the geometric zenith distance of the sun's centre reaches 90.8333°, and the fifty arcminutes of depression are the sun's own apparent radius, sixteen arcminutes, plus thirty-four arcminutes of atmospheric refraction at the horizon. Refraction lifts the disc into view before its centre has geometrically risen, and the sun is a disc rather than a point, so by the time you see the first sliver its centre is still below the true horizon. Both effects are already in the number.

The solar position itself is standard NOAA/Meeus geometry, the same ephemeris behind the sunrise and sun-position pages on this site. NOAA states its own accuracy: sunrise and sunset are theoretically good to within a minute between 72° north and 72° south, and within about ten minutes outside that. Keep that caveat next to the polar results below — the qualitative statements about high latitudes hold, but a printed time at 70° north is not a stopwatch.

Why the length varies so enormously

The golden band is ten degrees deep everywhere on Earth. What changes is the angle at which the sun crosses it. On the equator the sun's path meets the horizon almost vertically and it descends at about fifteen degrees an hour, so ten degrees takes forty minutes: run the calculator for Nairobi at the equinox and the morning golden hour is 06:24 to 07:04, forty minutes exactly, and that is the shortest it gets anywhere. Move north and the path tilts. At Los Angeles it is fifty-five minutes, at New York sixty-two, at Paris seventy-five, at Berlin eighty-six. Same ten degrees, a longer slanting route through them.

Push far enough north in June and the band stops being crossed at all. Run the calculator at 70° north on the June solstice and the sun's lowest point is 3.4°, inside the golden band, so it spends four hours and seven minutes there without setting. At 72° the lowest point is 5.4° and the golden total falls to two hours. At 72.5° it is 5.9° and forty-one minutes remain. At 72.6° the lowest point is 6.04° — just above the cut — and the golden hour is gone: the page reports that the sun does not cross the band on that day, which is the honest answer rather than an invented time.

Why the light changes colour

It is a path-length effect and nothing more exotic. Straight overhead a sunbeam passes through one atmosphere's worth of air; at five degrees above the horizon it passes through roughly ten times as much, and the relative air mass is still climbing steeply as the sun sinks — around 8.9 at the top of the golden band at six degrees, 14.6 at three degrees, and past thirty as the disc touches the horizon. That thickness does not dim the beam evenly. Rayleigh scattering removes short wavelengths far more efficiently than long ones, with an intensity going as one over the fourth power of the wavelength, so blue at 450 nanometres is scattered close to six times as strongly as red at 700. What survives the journey to your subject is orange and red.

The blue hour is the same physics with the direct beam removed. Once the sun is below the horizon nothing in the scene is lit by it directly; what reaches the ground is sunlight scattered downward by the upper atmosphere, and that scattered light is precisely the short-wavelength fraction the direct beam lost. The sky is not merely dim during the blue hour, it is a different illuminant with a different spectrum, which is why it renders skin and warm-lit windows the way it does and why a fixed white balance handles it badly.

Where the bands merge, vanish, or never end

Reykjavík on the June solstice is the clearest case of a band that does not behave. The sun's lowest point that day is −2.4°, which is inside the golden band and never reaches the blue one: the calculator reports six hours and forty-five minutes of golden hour and zero minutes of blue. There is no blue hour in Iceland in June, not because it is too bright but because the sun never gets low enough. Tromsø in December is the mirror image and stranger still: the sun never rises at all, its highest point is −3.1°, and yet the page reports two hours and twenty-five minutes of golden hour from 10:30 to 12:55, with a blue hour of fifty-eight minutes on each side. Polar night is not darkness; it is a long golden band with the sun just under the edge of the world.

One modelling consequence to know about before you read those totals. The tool segments a single local calendar day, midnight to midnight, so a band that runs across midnight is clipped at 24:00 and counted as two pieces of the same day rather than one continuous stretch of light. At Reykjavík in June this is exactly what happens: the golden hour shows as 00:00 to 04:52 and 22:07 to 24:00 on the same date, which is arithmetically right for that date and not the shape of the evening you will actually stand in. For anything near a pole, read the two neighbouring days together.

Planning: the window is a range, and the light is not spread evenly across it

Air mass climbs faster and faster as the sun sinks, so the last minutes of a golden hour do not look like the first. Take the Paris evening band, 21:08 to 22:23 on the June solstice. At the top of it the sun is at 5.98° and the relative air mass is about 8.9. Twenty minutes later it is at 3.16° and the air mass is 14.6. Twenty minutes after that it is grazing the horizon and past thirty. The colour shifts and the intensity falls over the whole hour, but most of both happens in the stretch nearest the horizon. If you are shooting one frame, the useful part of a seventy-five-minute band is the twenty or thirty minutes around the sun touching the horizon, not the middle of the block.

Two practical warnings the page carries and it is worth repeating. First, sunrise sits inside the golden band rather than at its edge, so arriving at the printed sunrise time means missing the first third of the morning window — at Paris on the solstice the golden hour opens at 05:21 and the sun clears the horizon at 05:47. Second, all times are in the UTC offset selected above the map. The city presets apply their own region's summer time to the date you picked, but if you type your own coordinates you own the offset, and an hour wrong there shifts every line on the page by an hour.

Frequently asked questions

What elevation angles does this calculator use?

Golden hour from +6° down to −4° of solar elevation, blue hour from −4° down to −6°, night below −6°, and sunrise and sunset as a separate threshold at −0.833°. The four are hard thresholds on the sun's geometric elevation, sampled once a minute across the local day and then bisected at every crossing, so a band that is crossed twice, once or not at all all come out of the same code without a special case for polar day. Note that the blue-hour floor at −6° is exactly the end of civil twilight as the US Naval Observatory defines it.

Why is golden hour forty minutes at the equator and over an hour further north?

Because the band is always ten degrees deep and the sun crosses it at a different angle. At the equator the sun's path meets the horizon almost vertically and it descends about fifteen degrees an hour, so ten degrees take forty minutes — the shortest golden hour available anywhere on Earth. Further from the equator the path is tilted, the sun travels a longer diagonal route through the same ten degrees, and the band stretches: fifty-five minutes at Los Angeles, sixty-two at New York, seventy-five at Paris, eighty-six at Berlin on the June solstice.

Why does sunrise fall in the middle of the golden hour instead of starting it?

Because they are set at different elevations. The golden band opens at −4°, four degrees before the sun's centre reaches the horizon, while sunrise is defined at −0.833°. The sun therefore spends several minutes inside the golden band while still geometrically below the horizon, lighting the sky and the tops of things before it lights you. At Paris on the June solstice the band opens at 05:21 and sunrise is at 05:47 — twenty-six minutes of usable light before the time on the forecast. Arrive at the printed sunrise and you have missed a third of the window.

Can there be a golden hour with no blue hour, or the other way round?

Yes, and the calculator shows both. Reykjavík on the June solstice has six hours and forty-five minutes of golden hour and no blue hour at all: the sun's lowest point that day is −2.4°, so it never reaches the −4° that opens the blue band. Tromsø in December is the opposite kind of oddity — the sun never rises, its highest point is −3.1°, and the page still reports two hours and twenty-five minutes of golden hour with fifty-eight minutes of blue on each side. Above 72.6° north at the June solstice neither happens, because the sun stays above +6° all day.

Is the light the same throughout the golden hour?

No, and this is the practical point the window hides. The colour comes from how much atmosphere the light has crossed, and that quantity accelerates as the sun sinks. Over the Paris evening band on the June solstice the sun goes from 5.98° to grazing the horizon, and the relative air mass climbs from about 8.9 to 14.6 at three degrees and past thirty at the horizon. So the second half of a golden hour is warmer, softer and dimmer than the first by a wide margin. Treat the printed window as when to be in position, and expect the frame you keep to come from the last twenty or thirty minutes of it.