Thierry Cohen’s Darkened Cities: World Skylines Without Light Pollution

What would Paris, New York or Hong Kong look like under a truly dark sky? French photographer Thierry Cohen answers with Villes éteintes (Darkened Cities), a series begun in 2010 that places the Milky Way above the world’s great cities. Each picture joins a city skyline with a star field photographed in a desert on the same latitude.

Thierry Cohen and the Darkened Cities series

Cohen was born in Paris in 1963 and began working as a photographer in 1985. He is regarded as a pioneer of digital photography: he says he was already working with digital techniques in 1986–87, in collaboration with Apple and Adobe, before digital cameras existed. His work has been shown at the Palais de Tokyo and the Musée de l’Homme in Paris, and in 2008 he was an official selection of the Mois de la Photo.

Since 2010 he has devoted himself to Darkened Cities. The series includes New York and San Francisco (2010), Rio de Janeiro and Tokyo (2011), Paris and Los Angeles (2012), and later London, Amsterdam and Chicago. Danziger Gallery in New York gave it a solo show in spring 2013.

How Cohen matches a desert sky to a city

The method rests on the rotation of the Earth. The stars that pass over a city during the night also pass, a few hours earlier or later, over every other place on the same latitude. So Cohen works in two steps:

1. He photographs the city, recording the exact time, camera angle, latitude and longitude.
2. He travels to a place on the same latitude with clear, unpolluted skies, such as the Mojave, Sahara or Atacama deserts, and photographs the sky facing the same direction.

The two images are then combined. For New York, the sky came from Nevada’s Black Rock Desert, home of the Burning Man festival, which Cohen picked as the best place in North America to see stars. For São Paulo, a city with few existing night photographs, he planned the shots in advance using photo records and Google Earth.

Cohen links his work to the 19th-century French photographer Gustave Le Gray, whose plates could not record sea and sky in one exposure. Le Gray made two negatives and joined them in the darkroom; Cohen does the same digitally.

The cost of light pollution

Cohen says he wanted “to make people aware that we’re not seeing any more stars”, showing the stars “that you should see if the lights of the cities were off”. Losing them, he argues, also narrows our questions about where we come from.

The numbers back him up. About 83 percent of the world’s population lives under light-polluted skies, including 99 percent of people in Europe and the United States. By 2016 roughly a third of humanity could no longer see the Milky Way from home. On the nine-level Bortle scale, astronomers say you need a level-four sky or darker to see it; level one is a pristine sky. DarkSky International, founded in the 1980s as the International Dark-Sky Association, campaigns for better outdoor lighting.

Hong Kong and Shanghai under the stars

The series also reaches Asia. Cohen travelled to Shanghai for the project, and his Shanghai and Hong Kong pictures show dense clusters of towers standing dark beneath a sky crowded with stars. Next to the familiar neon views of these harbour cities, the effect is striking.

To see a real dark sky, you have to leave the city: deserts, high mountains and designated dark-sky parks are the best places. Explore the projection behind a panoramic night sky or watch Teide in a landscape time-lapse.

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