In the photo, the shuttle and space station can clearly be seen as two separate spacecraft.
They appear as dark silhouettes in the upper right region of an otherwise bright yellow sun. Even the wings of Atlantis can be discerned along with the station's expansive solar arrays as both flew 200 miles (354 km) above Earth.
When Legault took the photo, Atlantis was flying below the space station and about to perform an orbital back flip so astronauts inside the station could snap high-resolution photos of the thousands of heat-resistant tiles lining the shuttle's belly.
Catching the scene is can be extremely tricky, Legault said.
"For me, besides having the right equipment for such a shot, the difficulty is to be perfectly prepared," Legault told SPACE.com in an e-mail. "This includes a lot of training and serious preparation."
It took just 1/2 a second for Atlantis and the space station to zip across the face of the sun. The solar crossing, called a transit, was only visible from a 3-mile (5-km) wide corridor beneath the flight path of both spaceships, Legault said.
"The excitement is like during a total eclipse, except that the [viewing corridor] is much smaller and the duration too," Legault explained. "So there is no chance of mistake. The possibility comes once only and if you miss it, it's over."
Legault learns of spacecraft transits from the website Calsky.com, which forecasts exactly when the events are visible and from where. He then carefully synchronizes his clock to Calsky's and heads out to the viewing area, which he selects using Google-Earth maps.
Weather forecasts for the region play a big part is selecting a prime viewing area, he explained.
When the actual transit time comes, Legault is not even looking through the camera. He looks at the clock, and then hits the shutter button to try and catch the spacecraft in flight.
"Also, there is a big excitement when I check all the images of the sequence ... to see if the space ship appears on one or two images (it cannot be on more than two)," Legault said. "At this moment, the image is just here for me and I can enjoy, before publishing it."
There are several chances for skywatchers in the United States see the shuttle and space station together with their unaided eyes. The two spacecraft have been docked since May 16 and can appear as bright as the planet Venus, weather permitting, to observers on Earth who know where to look. [How to spot the shuttle and station].
This isn't the first time Legault has captured the space shuttle Atlantis' silhouette as it flew before the sun, but it might be the last.
Atlantis' current mission to deliver a Russian room and spare parts to the space station is the orbiter's 32nd and final planned spaceflight. NASA plans to retire Atlantis and its two other shuttles after just three more missions, including this one under way now.
Legault last photographed Atlantis in front of the sun in May 2009, when it pulled up to the Hubble Space Telescope during NASA's final visit to overhaul the famed space observatory. Legault had watched Atlantis blast off from NASA's Kennedy Space Center in Florida a few days earlier.
"Atlantis is not especially my favorite for such shots, it's chance," Legault said, but added that Atlantis does feel special because he saw it launch in person last year. "And it's all the more special because it's its last flight.
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- Shuttle and Space Station Visible in Night Sky This Week