The Andromeda Galaxy (M31) is one of the jewels of the deep sky, fascinating both amateur and professional astronomers. Visible to the naked eye, it is nevertheless far from having revealed all its secrets. Thanks to new technological advances in amateur astrophotography, particularly the evolution of CMOS sensors, this celestial icon is now revealing itself in a wealth of detail.
This is precisely what the image taken by Cyril Richard, CNRS Research Engineer at the ICB Laboratory, offers us. Published on the cover of Astrosurf magazine (issue 133, March/April 2025), as well as in a double-page spread inside, this photograph marks a significant advance in capturing the fine structures of M31.
An extraordinary photograph
The most remarkable element of this image is the [OIII] arc, a very faint structure located next to the galaxy, discovered in 2023 by a team of amateur astronomers, whose origin remains a mystery. This signal, usually difficult to detect, is magnified here, revealing astonishing structures never before observed. Also visible is Andromeda Blossom, nestled in the galaxy’s arms, another flower-shaped structure whose origin remains equally unknown.
A work of expertise and precision
To achieve this result, a lengthy acquisition and processing process was required. The image was captured using a Takahashi FS 60 CB telescope, equipped with a focal reducer and an ASI2600MM camera, combined with 4.5 nm narrowband filters. The processing, carried out in collaboration with Philippe Bernhard, highlights the galaxy’s most subtle structures, thus illustrating the considerable progress of modern amateur astrophotography. It should be noted that part of the processing was done with Siril, open-source software, of which Cyril Richard is one of the main developers.
When art meets science
Astrophotography is as much a scientific approach as it is an artistic vision. Behind each image lies technique, patience, but also a true sensitivity to capture and reveal the beauty of the Universe.
🎙️ “I chose this target, which is very popular among amateur astrophotographers, because recently, a team of amateurs brought a fresh perspective by revealing new nebulae. So I wanted to take up this challenge myself. Indeed, this galaxy is probably one of the most photographed objects, as I mentioned. Yet it wasn’t until 2023 that a team of amateur astronomers discovered this vast cloud of gas, proof of its low visibility. The photograph you see here required extensive processing to make this cloud clearly visible. This discovery has been the subject of several scientific articles, which particularly motivated me. It was an opportunity for me to test my astrophotography equipment and see if I was capable of revealing the invisible.”
Cyril Richard
