Rob Sinclair’s nighttime image of Castle Geyser in Yellowstone National Park is proof that if a hydrothermal eruption happens and there are no tourists there to gawk at it, it’s still beautiful.

Shot in October 2006, the image is part of Sinclair’s ongoing, self-directed project to photograph the wonders of the national park system at night. "I’ve only done three parks, so I’ve got a long way to go," says the Sammamish, Wash.-based nature photographer.

Geysers in Yellowstone, which have been captured easily in countless tourist snapshots since the park opened in 1872, become particularly difficult subjects to photograph once the sun goes down and the mercury drops. Unlike its punctual cousin, Old Faithful, just a short hike away, Castle Geyser is an elusive spectacle...