He’s done it again, outdoing even his own incredible work.
Over the years, we’ve written many articles to share the beautiful and mind-bending astrophotography of Thierry Legault. Each year he seems to come up with ideas to try to surpass even his own craziest attempts of astrophotography feats – such as capturing spy satellites in orbit, or snapping pictures of the International Space Station (ISS) transiting the Sun during a solar eclipse.
Now, he was able to take pictures of the ISS transiting the Sun while two astronauts were doing a spacewalk. As an added challenge, Legault made sure he was in the right place at the right time so he could capture the ISS (and astronauts) while they were passing by three enormous sunspots.
WHAT??
On June 9, 2023 NASA astronauts Steve Bowen and Woody Hoburg performed a spacewalk to install a new set of iROSA solar panels.
“For the occasion, I drove 6 hours from home to go to the Netherlands where a transit happened one hour after the spacewalk started,” Legault said on Facebook. “This time, the ISS passed in front of 3 sunspots groups in a split second! The big sunspot could swallow the Earth, but it is 300,000 times farther than the ISS (150 million km versus 550 km).”
In a previous Universe Today article, Legault explained how he studies maps, and will travel thousands of kilometers to be in the right place to capture such a transit. He uses a radio synchronized watch to know very accurately when the transit event will happen.
How did he figure out when the ISS was going to be passing in front of the current batch of sunspots?
“Using real time images of the Sun, I estimated the position of the main sunspot groups towards vertical and horizontal directions –which depends on time and location,” he told Universe Today. “I compared it to the trajectory planned by www.transit-finder.com, and I tried to place myself on the corresponding transit position.”
For a transit event, he gets get a total of 16 images – 4 images every second, and only after he enlarges the images does he know if he succeeded or not.
Legault said all the individual images are single shots at 1/32000s. None of his image of ISS transits are stacked. His camera has a continuous shuttering for 4 seconds, and he begins the imaging sequence 2 seconds before the calculated time.
Back in 2011, Legault was able to take pictures of Steve Bowen on another spacewalk, as the ISS passed in front of the Sun. When he learned Bowen was on another spacewalk, Legault had the idea to try and get a picture of him again.
“Oops, I did it again…better!” Legault said on Facebook.
Keep in mind, an ISS transit lasts less than a second – this one was just 0.75 seconds long — and is shown in slow motion on Facebook here.
Capturing the event in images must be timed with ultimate precision as the ISS is traveling at 27,000 km/h (17,000 mph).
His instruments were an CFF200 apo refractor, Baader Herschel wedge, Olympus OM-1 at 1/32000s, and fellow astrophotographer Emmanuel Rietsch’s GPS trigger. Legault also thanked friend Charline Giroud for assistance in the setup.
Check out Thierry’s website to see more of his wonderful work.