It's been said that the night skies are the other half of the National Park System. And it only makes sense, for when you're in a park and the sun goes down you tend to look into the night sky to spot constellations or, if you're lucky enough and in the right place, a comet overhead.

Keeping that other half of the park system in mind, today's podcast will be a somewhat dark one. Our guest is Jeff Pfaller, a fine arts photographer who spent five years capturing night skies over national parks and other public lands.

A book coming out in October by Pfaller showcases synchronous fireflies at Great Smoky Mountains National Park, the famous illumination that makes Horsetail Fall in Yosemite National Park look like a cascading stream of lava, a shot of the whirling Milky Way against a colorful stump of petrified wood at Petrified Forest National Park, and many other nighttime images that remind us of that other half of the park system is overhead.

National Parks Traveler readers can obtain a $15 discount on the book's purchase price by using this link to order it.