Capturing the ISS as it transits the Sun or the Moon is one of the holy grails of every astrophotographer. But how about capturing it as it transits the Sun and a massive sunspot, in the middle of a spacewalk? Thierry Legault has an answer to this question – that’s extremely exciting and you need to be extremely precise, plan ahead, and be at the right place at the right time. We chatted with Thierry about his stunning transition image, and he shared some details about this impressive shot, as well as many interesting details from his rich astrophotography career.
Thierry’s astrophotography beginnings
I first wanted to know what drew Thierry towards astrophotography, particularly capturing rare events like this. I learned that he is neither an astronomer nor a photographer (I mean, officially) – he’s an engineer. But he’s been into astrophotography since before I was born, and he talks about it with so much knowledge and so much passion, that it was a real treat listening to him.
Thierry reveals that astrophotography has always fascinated him. It all started when he was a teenager and got his hands on a small telescope. Back then, I would take photos with silver film, since it was back in the 1970s. But everything changed when digital sensors came into the picture in the early 90s. It was a revolution in astronomy, and he tells DIYP that he just couldn’t resist experimenting with this new technology.
“I acquired my first digital sensor in 1993, although there still wasn’t a standard digital camera available in stores. It was a specialized camera with a digital sensor, similar to what we have today. This camera allowed me to do things that even professional astronomers couldn’t do back in the 60s or 70s. It was truly amazing, but only a few of us had access to such sensors due to their high cost and complexity.”
One of his first notable astrophotography achievements was capturing the International Space Station in front of the sun. He used a camera that took one image every 30 seconds, and since the transit only lasts a few seconds, you can imagine how challenging this was. “Back then, technological progress was still relatively recent, so I had to figure out many things on my own,” Thierry recalls. “Throughout the 90s, I encountered numerous obstacles and faced a steep learning curve. However, I persisted and continued to capture breathtaking images of celestial objects, including the Moon and planets.”
The astrophotography books
Other than taking magnificent photos and showing great interest and knowledge in astrophotography, Thierry also wrote three books on the subject. “Around 2003, I received suggestions from many people, urging me to write a book about astrophotography,” he tells DIYP. “So in 2006, I published my first book, which was a concise guide to astrophotography.”
The book received a good response and was subsequently translated from French into German, Spanish, and English. Despite the success of the book, he never stopped exploring astrophotography and setting new challenges for himself. “I constantly ask myself, ‘Can you capture this?’ How about that?’ Not every attempt was successful, but the thrill of the chase and the occasional triumphs have kept me going.”
Planning the shot
As you can probably imagine, it takes a lot of planning for capturing such a short moment like a spacewalk during the ISS transition. So, I asked Thierry about what it involved and how he managed to plan everything perfectly even the weather. For this particular image, Thierry drove from his home near Paris all the way to the Netherlands, to the south of Amsterdam.
“I rely on websites like transit-finder.com to determine when and where a transit will be visible. The transit path long, but it’s very narrow, often spanning only a few kilometers, and being at the exact place and time is crucial. You have around 500m available, and you need to find the right spot: you can’t stand in the middle of the road, for example. Or in the forest, because the trees will block your view.
So I search for a suitable location along the transit line, considering factors like ease of access and minimizing interference. It can take hours to find the perfect spot, especially in unfamiliar territory. Additionally, I closely monitor weather forecasts, specifically cloud coverage, to ensure optimal conditions for capturing the event.”
Thierry told me that he can’t even count how many times he missed eclipses and other important events because of the clouds (oh, so familiar). In 2008, he went to Siberia to shoot a solar eclipse – and at the very moment he’d been waiting for, there was a single cloud covering the sun during the totality. What a bummer! This is why he monitors the weather forecast with particular attention, focusing on cloud coverage above all else.
Thankfully, there were no clouds when he was taking his latest transition image. The Sun is currently very active, so he also captured a big sunspot. It’s big enough that it could swallow the Earth, but it is 30,0000 times farther than the ISS (150 million km versus 550 km). Just so you get the idea.
The biggest challenges
Other than meticulous planning and finding the perfect spot in an unknown location, Thierry also faced some challenges when he set everything up and was ready to shoot. “Technical challenges are an integral part of astrophotography,” he tells DIYP, “and capturing such rare events requires precision.” One of the biggest challenges is manual focus. Yup, you have to focus manually, with a requirement of 1/20th of a millimeter accuracy at least. It becomes even more difficult when the sun is high in the sky, causing constant image fluctuations due to turbulence. Nevertheless, with loads of practice and great familiarity with his equipment, Thierry has developed techniques to tackle these challenges and take nice and sharp photos.
The technicalities: gear, settings, and editing
Believe it or now, all the individual images are single shots, shot at the incredible 1/32,000 s. “I never make ISS transits with stackings or assemblies,” Thierry notes. He sees no challenge in that, so he rather focuses to get everything right in-camera. For this image, he used a CFF200 triplet apo refractor telescope, Baader Herschel wedge, Olympus OM-1 camera, and Emmanuel Rietsch’s GPS trigger.
Once the image is captured, post-processing is relatively straightforward. “I select the best image from the sequence and make minor adjustments to parameters like contrast and sharpening using software like Photoshop. I aim to keep my images as natural as possible, without extensive editing or manipulation. I want them to represent what we could visually perceive if we could observe the event in real-time, albeit at a slower pace.”
The sense of accomplishment
What goes through your mind when you first see that you managed to capture the image you had had in your mind? This is something I’d ask every photographer, and I also asked Thierry.
“When I finally see that I’ve successfully captured the image I envisioned, a rush of joy and satisfaction overwhelms me. The culmination of all the planning, technical prowess, and perseverance is incredibly rewarding.”
In our conversation, he recalled the time in 2009 when he captured the transit of the Atlantis space shuttle across the Sun just 24 hours after attending its launch. The camera he had at the time was running at 4 frames per second, and the transit was one-quarter of one second. He literally had one shot!
“I wasn’t even sure that I would capture it, but I triggered the camera and tried. When I removed the camera, I looked through the series of images on the camera screen. I looked at them one by one – nothing. But then I saw something. I zoomed in, and there it was – at the very edge of the sun. The image made it to the front page of The Times, and the sense of accomplishment was indescribable.”
Safety measures when photographing the sun
Thierry’s passion for astrophotography is contagious, and I wanted to take photos of the sun myself (I don’t even have to capture the ISS). :) So if you feel inspired too, we have to talk safety! For photographing the sun safely you must use special solar filters for both the telescope and the camera. “Without these filters, the intense sunlight would damage the equipment,” Thierry warns. “I use a specific solar filter that allows me to work at high shutter speeds, as low as 1/32,000 second. This allows for short exposure times, minimizing any potential blurring caused by atmospheric turbulence.”
Final word – advice to aspiring astrophotographers
At the end of our conversation, Thierry shared some words of wisdom for all aspiring astrophotographers hoping to capture this or any other celestial events.
“I would encourage them to become familiar with their gear and invest in a good solar filter for photographing the sun safely. Remember, practice is key, and by persevering through challenges and honing your skills, you can achieve remarkable results. While luck does play a role, the satisfaction of capturing these rare events is well worth the effort. So, embrace the challenges, learn from each experience, and keep pushing the boundaries of astrophotography!”
I truly hope that you enjoyed reading about Thierry’s photos as much as I enjoyed talking to him about them. Be sure to find more of his amazing work on his website and follow him on Facebook and his YouTube channel.