Astrophotography

When Pettit tried to take pictures of city lights he quickly realized it wasn't as easy as photographing the stars. The station, traveling 17,500 mph, races around Earth in only 90 minutes. Lights on Earth's surface move through the window too quickly for long exposures. Stars, on the other hand, appear nearly motionless because they're so far away. It's like driving down a highway in a fast-moving car: Distant mountains and trees don't appear to move much, but the fringe of the road is a blur.

"I needed something to help me track the city lights, to cancel the orbital motion of the station."

Don Pettit's homemade "barn door tracker" onboard the ISS.

I assembled a 'barn door tracker'," says Pettit. "It's based on the fine gimbal movements in the IMAX camera mount for the Destiny Lab window. I figured out a way to mount a threaded screw and nut (scavenged from a Progress rocket) and drive it with a Makita drill driver." The drill turns the screw, which moves the camera and its spotting scope. "All of these modifications clamp on to the IMAX mount and do not change its original function in any way," notes Pettit.

"I manually compensate for the station's motion by looking through the spotting scope and running the drill at the same time. It takes a bit of practice, but you do learn to track."

Pettit has since photographed cities and towns around the world. "With tracking we can see individual city blocks - no blurring." Some towns are well-organized like checkerboards. Others are more ... organic. London, for example, resembles a glittering luminous spider web splayed across the landscape. "Really nice," says Pettit.

For sheer beauty, though, "my favourite is still auroras," he says. "I can't get enough of them."

more London, England, photographed by Don Pettit from Earth orbit in February, 2003.

Pettit is scheduled to remain onboard the ISS until May 2003. Until then, in his spare time, he plans to continue taking pictures and sending them to Earth. There'll be more auroras, more meteors and star clouds and city lights.

And probably lots more nose prints on the window....