At Trevor Paglen’s website:
A number of military bases and installations exist in some of the remotest parts of the United States, hidden deep in western deserts and buffered by dozens of miles of restricted land. Many of these sites are so remote, in fact, that there is nowhere on Earth where a civilian might be able to see them with an unaided eye. In order to produce images of these remote and hidden landscapes, therefore, some unorthodox viewing and imaging techniques are required.
Limit-telephotography involves photographing landscapes that cannot be seen with the unaided eye. The technique employs high powered telescopes whose focal lengths range between 1300mm and 7000mm. At this level of magnification, hidden aspects of the landscape become apparent.
Limit-telephotography most closely resembles astrophotography, a technique that astronomers use to photograph objects that might be trillions of miles from Earth. In some ways, however, it is easier to photograph the depths of the solar system than it is to photograph the recesses of the military industrial complex. Between Earth and Jupiter (500 million miles away), for example, there are about five miles of thick, breathable atmosphere. In contrast, there are upwards of forty miles of thick atmosphere between an observer and the sites depicted in this series.