Pascal Hilkens Astro Page

Pascal Hilkens en Walter Swinnen

It is June 21 and the longest day of the year, when I go to pick up Walter at 7am. A few minutes later we leave for an 800km ride towards Serbannes, located in the Auvergne-Rhone-Alpes region near Vichy. And all this with the intention of participating in the two-day “Les Rencontres des Observateurs Solaires”. This meeting is organized every 2 years by a collective of astronomy enthusiasts around Patrick Pelletier who have a passion for the sun.

Due to the extra stops for electric charging, road works, traffic jams and 100km of country roads, it takes us 12 hours and we are just in time for a joint lunch. Together with 50 other ROS participants we sit at the table and enjoy our glass of red wine. The first conversations are difficult and somewhat awkward because only French is spoken. Not such a problem for Walter who does this every day, but for me it was several years ago. We immediately meet the organizer, Patrick Pelletier, which makes us feel a little more at ease.

Pascal with Patrick Pelletier

At the table, I see some participants wearing a T-shirt from the 2017 eclipse in Idaho (USA). I almost fall off my chair when I hear that they were present in Rexburg. So I was at the same place with my family and I still remember vividly when the bus with French people arrived in the morning and they immediately marked out their area with red and white tape. Quite hilarious and so the first conversations were about the 2017 and 2024 eclipses in Texas. Just after 9:00 PM we leave for our apartment in Vichy. It is quiet along the way because the European Championship match between France and the Netherlands is being played. It is difficult to find a parking space, but that is not because of the European Championship match but because of the Olympic flame, which stopped in Vichy in the afternoon. After installation in our apartment, we still watch the European Championship match, although our eyes close regularly.

After a tasty breakfast we leave back towards Serbannes for the first of two days of conference. We now have 120 participants and immediately see the various stands of Azure3Dprint, AstroSurf and Medas Instruments. Furthermore, several telescopes have already been set up on the lawn, but for the time being they are still covered in plastic because the weather is not really great.

In the meantime we are introduced to Valerie Desnoux, it is she who developed the Inti software for the Sol'ex. I will speak to her a few more times during this conference.

Pascal with Valerie Desnoux

After lunch the conference starts and there are numerous topics on the agenda:

· Saterday June 22

o Christian Viladrich: Test de filtres / imagerie avec les nouveaux filtres UV,

o Jérôme Bastardie: Fonctionnement du Sol'Ex avec animations 3D,

o Laszlö Francsics: Nouveau télescope solaire Soleye 300 mm,

o Valérie Desnoux, Christian Buil, Guillaume Bertrand : Présentation du spectrohéliographe Sol'Ex et du projet SunScan,

o Florence Cornu CNRS Bilan ProAm spectrotrohéliographe Sol'Ex,

o Christian Viladrich: Méthodes pour traiter les images de l'éclipse 8/4/24,

· Sunday June 23

o François Rouvière:: Sol'Ex et résolution,

o Xavier Dequevy: Le programme Climso aujourd'hui.

Christian Viladrich, editor of the book “Solar Astronomy”, explains how to measure FWHM values of H-alpha filter using a Sol'Ex. In conclusion, he states that the measured values of H-alfa air etalons filters correspond to those shown by the manufacturers. However, this is not the case for the H-alfa mica etalon filters; the values shown by the manufacturers give a smaller FWHM value than that measured with the Sol'ex.

Pascal and Christian Villadrich

Jerome Bastardie's turn comes next and he has found a solution on how to present the operation of the Sol'ex. With the help of a 3D animation, it now becomes much clearer how a sol'ex actually works. Nicely done and I will definitely use it. What I found even more interesting was his overview of the 10 most common start-up problems with the Sol'ex. These 10 problems are shown graphically with an indication of the solution.

Walter with Jerome Bastardie and Solex version 2

Lazlö Francsics, a young architect, inventor and renowned astrophotographer, came especially from Hungary. He presents his new next generation Soleye 300 telescope to the public for the very first time, making it a real world first. He talks passionately about how everything started, including the search for a suitable observation location for the sun. He eventually found it near a lake that is about 2km wide. Depending on where the wind is blowing, he will photograph the sun on either one side of the lake or the other. He claims that at this spot on the lake the turbulence is so negligible that there is a 100% chance of a good photo. If he had the perfect optics, this should lead to beautiful shots of details of the sun. He then started building a 300mm f/4 telescope with a primary non-crystalline SiO2 mirror. This mirror is provided by his company with a coating (Optical Interference Coating) that is sensitive to both red and violet light. Both the mirror and the special construction of the telescope can withstand the heat of the sun. The result is a resolution of 0.28 arcseconds, which means that recordings of 0.35ms can be made. For recordings in H-alpha such as CaH or CaK, a filter can also be placed in this wavelength. Lazlö shows some of his photos at the end of the presentation and they simply blow you away.

Lazlo Francsics with solar scope and Walter in the back

Soleye 300

Then it was the turn of the Sol'ex grandmaster himself, Christian Buil. Together with Bertrand Guillaume, they present their Sunscan heliospectrometer in public for the first time, again a world first. The difference with the sol'ex is that the device is equipped with an f/125mm lens, a built-in camera (IMX219/708) and built-in Raspberry Pi. The latter controls the camera, takes care of the processing using Inti and sends the images to your smartphone. The grid (2400l/mm) and the slit (10micron) are the same as those of the sol'ex. With the Sunscan they initially want to provide a device for educational purposes. The resolution is lower than the sol'ex, but using it is much easier due to the connection from the raspberry pi to your smartphone via an app. Images of the sun are sent directly to your smartphone, which is a plus for public presentations.

Pascal and Christian Buil

Sunscan System

Florence Cornu, affiliated with the Observatoir de Paris and co-founder of the Pro-Am Sol'ex observations for the Bass2000 database, calls on amateurs who want to participate with their Sol'ex in observing the H-alpha line, H- alpha 2cb and Ca H and K line. Currently there are about 25 amateurs participating, exclusively men and almost all but a few French. You can register via

https://dio.obspm.fr/Syst%C3%A8me_et_r%C3%A9seau/Transfert_de_fichiers/. With the cooperation of amateurs, the aim is to guarantee the continuity of sun observations. There are always times when the sun cannot be seen by pros, such as cloud cover, and which can then be caught by amateurs.

It was then time to stretch our legs and since there were some clear skies we could also take a look through the different types of telescopes that were set up. A quick group photo and after eating dinner it was time for a final presentation. This coincided with our European Championship match Belgium-Romania; luckily my wife kept me informed.

Christian Villadrich explains how he automatically edited his many hundreds of photos of the April 8, 2024 eclipse. The challenges :

Many hundreds of photos
Centering the photos
Stacking the photos
Editing the photos taking into account the enormous gradient between the sun's disk, sun's edge and corona.

I must say that the result is astonishing. I almost fell off my chair when I saw the result. The corona is visible from the edge of the sun far beyond. And because images were taken from contact 2 to contact 3, the movement of the low corona could even be visualized. Unique! Since I also have some photos of this and previous eclipses, I should consider this process.

Solar Eclipse April 8, 2024 Edited by C. Villadrich

In the meantime, the Red Devils had won, and it was time to go to our apartment.

Day 2: we got up on time because there were actually some clear skies. We arrived around 9:30 am and there were a lot of people behind and around the telescopes. The ideal time to compare between Lunt and Coronado's and between single, double and triple stacked filters. The sunscan was set up next to various sol'ex versions as well as coronographs. We were short of hands and eyes and a lot of information was exchanged. For example, I learned that the Sol'Ex 2.0 and pro version is more stable than the v1 version; According to Valerie Desnoux, the Sol'ex “sawtooth effect” is the result of the scanning itself (and therefore of the mount) of the sun rather than the turbulence factor. I must say that I saw almost no sawtooth effect among those present; wouldn't there be turbulence at that place? I did see that many had a SW AM3 mount. A nice fact is that you can have Inti start with the last recording made instead of having to restart the process every time.

Coronograph

Facts! We had a chat with Christian Buil and I understand that about 1000 Sol'exes have currently been sold, of which about 800 are for sun observations, the others are Starex applications. A conversation with Christian Villadrich about the use of a SCSM (Solar Scintilation Seeing Monitor) confirms that this is a plus, but that we have to make it ourselves (read Walter). At the AstroSurf stand we were introduced to the new version of the Astronomy Solar book. The new version contains a lot of new material and is therefore 50 pages thicker. Walter has bought two versions, I am waiting for the reworked English version that should be released in the middle of next year. I finally decided to buy the pro version of Sol'ex.

Furthermore, two triple stacked H-alpha telescopes were set up. Each with two front coronado air etalons and a back Lunt 40mm etalon unit. One version with a Baader telecentric lens TZ4 system, the other without. Explanation about this version can also be found in the Solar Astronomy book. By comparing between a double and a triple stack, I can conclude that the triple brings out even more details. Not as spectacular a difference as between a single and double stacked.

Triple H-alpha Stack with Telecentric TZ4 lens

A few used a Hinode Solar Guide to track the sun. Installation was easy, just plug the cable into the guiding port of the Skywatcher mount. After some research it turns out that it is no longer available... I have to investigate this further. Finally, I thought placing a screen just in front of the eyepiece was a good idea for easy sun observation. This instead of a towel over your head.

Walter and HinodeSolar Guide

Time for our last lunch and then some more lectures.

François Rouvière provides information about the Sol'ex and possible improvements to increase resolution. Examples to increase the resolution are:

Stacking images
Larger diameter of the telescope; results from 100mm refractor provide greater resolutions and images are assembled into one image via Inti Mosaic
Use of larger diffraction grating; 50x50mm instead of 25x25mm. And use a wider objective before and after the grid

The last lecture is about project Climso, 4 instruments that are installed on the Pic du Midi. Recordings in H-alpha and Ca-K and two coronographs.

This concluded the two-day ROS conference. We said goodbye and drove back to our apartment. We walked some more through Vichy to stop in a sports café for our last supper. Once back in our apartment we took the time to catch up while watching the European Championship match Switzerland-Germany... with a Brugse Zot.

On Monday morning we left for home just after 7:15 am and we both agreed that it was a successful meeting where we learned a lot and were able to make new connections.