People come to the dunes for the sunset and stay up for the sky, and the two are very different experiences. A desert night is not just a dark version of the night at home. It is a different sky, with more in it than most people have ever seen. This is what is actually up there above Erg Chegaga, and how to plan a night around it.
Why the desert sky is different
The first thing to understand is that darkness is a resource, and it is scarce. Light pollution spreads far beyond the cities that create it. Studies estimate that 83% of the world's population lives under light-polluted skies, that around 80% of North Americans and about 60% of Europeans can no longer see the Milky Way at all, and that roughly a third of humanity cannot see it from where they live.
At Erg Chegaga you are hundreds of kilometres from the nearest large city, with no village at the foot of the dunes and no passing traffic. On a moonless night the sky there is as close to a natural night as most people will ever stand under.
Reading the sky: the Bortle scale
Astronomers describe how dark a sky is with the Bortle scale, running from Class 1 (the darkest) to Class 9 (a city centre). The scale matters because the same sky reveals different things at different levels.
At Class 1, the description is almost hard to believe until you see it: the zodiacal light is visible and even colourful, the faint gegenschein is there, and the brighter regions of the Milky Way cast obvious shadows. At Class 2, a truly dark site, the Milky Way is still richly detailed. To see our own galaxy at all, you generally need a site at Class 4 or better, already far beyond what most towns offer.
What you will actually see
On a good moonless night at the dunes, the Milky Way is not a faint smear but a structured band running from horizon to horizon, dense with dust lanes between the stars of Scorpius and Sagittarius. Look up for long enough and you will catch shooting stars without trying, and the sky seems to change as your eyes darken over the first fifteen minutes.
That adaptation is the one thing you cannot rush. Give your eyes twenty minutes away from any white light and the whole scene deepens.
The zodiacal light and the false dawn
The strangest thing in the desert sky is one most people have never heard of. The zodiacal light is a faint, soft glow caused by sunlight scattering off dust between the planets. It looks like a pale cone of light rising from the horizon, easily mistaken for the glow of a distant town that is not there.
It is best seen in the weeks around the equinoxes: after dusk in spring, before dawn in autumn. This pre-dawn glow has a long history as the "false dawn", known in Arabic as al-fajr al-kādhib, distinguished in tradition from the true dawn because it rises vertically rather than spreading across the horizon, a distinction once used to time the first prayer of the day.
Timing your night
Two things decide what you see: the moon and the season. A full moon floods the sky and hides almost everything worth looking at, so we plan dune camps away from it when guests come for the stars. The new moon is your window.
The season matters too. Summer nights are warm and the core of the Milky Way is at its most brilliant; winter nights are colder but clear and long. Our month-by-month guide to the Moroccan Sahara walks through how the year changes the trip.
Where we watch
Our two-day bivouac night at Erg Chegaga is the shortest way to stand under this sky, built around a single night at the dunes. Our four-day camel route across the hamada and erg gives you several nights away from any light, and our one-night trip covers the highlights if your time is short. Bring a warm layer, give your eyes time, and look up.
Sources
- The Bortle scale: classes, zodiacal light, gegenschein and Milky Way shadows at Class 1, Wikipedia, Bortle scale
- Light pollution: share of population under light-polluted skies and the Milky Way visibility figures, Wikipedia, Light pollution
- Zodiacal light: cause, best seasons and the "false dawn", Wikipedia, Zodiacal light
