Star Trails over the Titan

One of the most intriguing aspects of photography is its ability to show us phenomena we cannot see with our unaided eyes. For example, our eyes cannot integrate all the light that enters them over a period of hours into a single image. Cameras, however, can. We’re all familiar with the way celestial objects such as the sun and moon appear to rise in the east and set in the west. Many stars follow a similar trajectory. Less obvious are the patterns made by stars near Polaris, the North Star. Stars within an angular distance of Polaris equal to the latitude of the observer are said to be circumpolar: they never rise or set, but instead circle endlessly around Polaris. For example, at the latitude of Boulder, 40 degrees north, all stars within a circle centered on Polaris with an angular radius of 40 degrees are circumpolar. A long exposure at night reveals the graceful concentric circles these stars make as they rotate around Polaris.

Modern digital cameras can also record color at night in a way that my eyes cannot, no matter how dark-adapted I become. Moonlight, for example, is actually warmer in color (more yellow) than noon daylight. Photographs of star trails over a moonlit landscape obviously cannot be a literal record of what I saw; instead, they are an illustration of the power of the camera to show us the world in a unique and surprising way.

In August 2016 I went to the Fisher Towers, in southeast Utah, to shoot the Perseid meteor shower. While there I decided to set up a second camera to shoot star trails. The moon, which was 65 percent illuminated, provided the light on the land. In the film era, you could make a single exposure lasting several hours to record star trails. Digital cameras, unfortunately, generate unmanageable noise if you attempt an exposure that long. The digital solution is to shoot many frames, back-to-back, then combine all the images in software to create the star trails. Using a 16-35mm lens set to 16mm, I shot 340 frames at 1 minute, f/2.8, ISO 200, then used a Photoshop script written by nature photographer Floris van Breugel to create this image of star trails wheeling over the Titan, reputedly the tallest freestanding natural tower in the United States.