Not too many years ago Harold Davis was camping out in the Sierras, looking up at the stars above the sequoias and thinking that he'd never really seen a photograph that came close to capturing what he was seeing.

How would I go about taking that photograph, he wondered.

It took a while, but he figured it out.

"My first efforts were awful," he says. "Intuitively, what you think you should do when looking at something very dark is boost the hell out of the ISO." Actually, the opposite is true; all save one of the photos you see here were taken at ISO 100. It's exposure time, not ISO, that's a key to night photography.

Starting with trial and error and building on growing experience, he worked out some general exposure guidelines and starting points for his night images. For ever-popular car light trails, exposures of eight to ten seconds; longer if you like your light trails to look more solid. A good starting point for street scenes and cityscapes: 30 seconds. Landscapes with star trails call for at least three or four minutes, but for pronounced "as the earth turns" trails, figure 20 minutes to hours in length.

But as you approach hours, noise becomes a huge issue. To solve the problem, Harold applied an astronomical photography technique. His photo, Edge of Night, is the result of a combined exposure time of about an hour, but instead of shooting one hour-long, noise-building image, he shot 20 three-minute exposures and stacked them in post production.

Equipment plays a key role in Harold's night photography. A sturdy tripod goes without saying. Then, because 30 seconds is the longest shutter speed most cameras allow, Harold uses a Nikon MC-36 Multi-Function Remote Cord and the camera's bulb function to keep the shutter open for as long as he chooses. The MC-36 will also trigger the camera and allow him to program the shutter release and shutter release intervals.