Pascal Hilkens and Walter Swinnen
It’s June 21st and the official start of summer—and you can feel it, as it promises to be sunny and hot. On Friday evening, I had already packed the car with my suitcase of clothes, mounting equipment, telescope, and Sol’Ex. Johan L also stopped by briefly to deliver the new Sol’Ex (a new design by James R) that he had printed during the week. The device is 3D-printed in matte black material and looks very professional because of it.
After a short night’s sleep, I set off at 5:15 a.m. towards Diest to pick up Walter. And so we left at 5:30 a.m. heading to Baron (in the Oise department of the Hauts-de-France region), about 45 km northeast of Paris. It’s a 340 km drive, and we took the route through Brussels toward Mons and Valenciennes. After two hours of driving, we stopped near Cambrai for a pastry and a cup of coffee. After some issues, I finally managed to charge my electric car. Satisfied, we continued on our way and approached the first toll station. The toll is always a tense moment—will the Bip&Go work or not? And yes, everything worked fine.
I thought I had set the GPS to the exact location, but when it led us into the forest, we double-checked everything. After entering "Baron center," we were back on the right track.
In the village, a few signposts guide us to the location. We arrive right on time, and in the meadow next to the soccer field, there's already a pleasant buzz of activity. We register and are treated to a cup of coffee. From this point on, it's all French being spoken, which definitely takes some getting used to. We introduce ourselves and walk past the many set-up (solar) telescopes.
The program is changed, and Olivier Aguerre begins with his lecture on observing magnetic fields and the E-Corona using the Sol’Ex. He shares his experiences with us, and we get the chance to ask quite a few questions. Then it's time for lunch, and we sit at the table with Christian Buil and Valérie Desnoux. During our conversation, it becomes clear that the Sol’Ex collimator can be refocused when changing the wavelength. I had tested this before the meeting with very good results and was glad that Christian could confirm it. He admitted that he doesn’t talk much about this, as the Sol’Ex is a device that involves quite a few compromises.
One thing led to another, and I was able to hand over the new Sol’Ex by James R to Buil. He was very impressed by the print quality and the design. The device quickly made the rounds. Buil didn’t waste any time and took a lot of photos.
The next speaker is Dr. Allan Sacha Brun, an astrophysicist working at CEA (Commissariat for Atomic Energy and Alternative Energies), who takes us on a journey through the fascinating world of solar phenomena.
After the lecture, I set up my Sol’Ex setup and manage to take some recordings and compare them with others.
We continue exploring the various setups, many of which feature very impressive equipment.
Several participants have double and even triple-stacked H-alpha telescopes. All of them have placed a circular polarizer between the H-alpha filters. In the meadow, there are also some participants using the same AZ/EQ6 mount, and they confirm that scanning is only possible in one direction. In the other direction, it is not possible to perform vibration-free scanning. There are also a few harmonic mounts present, with the note that the scan speed may vary during acquisition. This is a kind of built-in safeguard that must be taken into account.
I take some time to talk with Florence Cornu, who is the program leader of Sol’Ex Pro-Am SOLAP, of which I am a member. She informs me that submitted images will be judged more strictly in terms of tilt deviation. Therefore, polar alignment and the Sol’Ex setup will need to be nearly perfect.
I check with Christian Viladrich on the status of the new edition of his book Solar Astronomy. According to the latest updates, he expects it to be ready in the first quarter of 2026.
It is now 7:00 PM, and the organizers (MARS60 – Mouvement Astronomique de la Région de Senlis) treat us to a snack and a drink. A little later, we sit down for dinner. This time, we’re at a table with Nic Spencer (Citizen Solar Astronomer, York, UK), Michael O’Connell (former Chairman of the Irish Federation of Astronomical Societies, Kildare, Ireland), and Filip Szczerek (better known as GreatAttractor and developer of IMPPG), with many interesting conversations.
After dinner, we drive to Senlis where we will spend the night at Hotel Grill Camp. It’s a fairly basic hotel, but it's only for one night. I’m also able to charge my car there. We sleep well, as it had been a long and tiring day—especially with temperatures reaching around 37°C.
In the morning, we enjoy a hearty breakfast and, after checking out, we drive back to Baron.
The weather is somewhat changeable, with occasional threatening clouds, but it remains dry. We meet up with Olivier to go over the practical side of capturing a magnetogram of the Sun. I have all the necessary equipment with me, which allows us to sort everything out fairly well.
I also speak with Valérie Desnoux about her software Inti and some issues I’ve encountered. She mentions that she is currently working on a newer version, and we manage to solve a few problems together. Afterward, Valérie and Christian Buil give a presentation on SunScan—the smaller sibling of the Sol’Ex, mainly intended for public outreach. The SunScan uses the same diffraction grating as the Sol’Ex and also features a built-in camera and Raspberry Pi. The images are transmitted via Wi-Fi to one or more smartphones. This last feature could be particularly useful for public demonstrations. I forward the information to Johan L, who expresses interest.
During lunch, we sit with Nicolas Godingen, a Frenchman currently working and living in Belgium. He focuses primarily on solar photography using mirror telescopes, whose mirrors have a special coating. These coatings are designed to primarily transmit H-alpha and Ca II wavelengths. He speaks very highly of the coating company MCM (
https://www.mcm-optique.com/fr/). To reduce costs, several mirrors can be treated simultaneously in a vacuum chamber. I glance over at Walter—perhaps this is something for the future?
We attend another lecture by Christian Viladrich and Thierry Legault, who go each year to Saint-Véran for a week of solar photography. The location is at an altitude of 2000 meters, offering sunshine almost every day and excellent seeing conditions. They use telescopes with mirrors coated specifically to transmit only H-alpha and Ca II, as well as triple-stacked H-alpha telescopes. Their images and videos are absolutely stunning.
We take one last walk around the field, say our goodbyes to the participants, and if all goes well, we’ll see each other again at ROS 2026 (Rencontres des Observateurs Solaires) in Serbannes on June 13 and 14, 2026.
We head home, and with smooth traffic, we arrive around 7 PM—tired but satisfied.
