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| PRO-AM Group | JASON2025 |
Systematic observations of the solar chromosphere and photosphere began 117 years ago at the Meudon Observatory with the spectroheliograph developed by Deslandres. Since then, an exceptional collection of more than 90,000 monochromatic images in Ca II K and Hα has been built up, covering over 11 solar cycles. This unique dataset is made available to the international scientific community through the BASS2000 database.
In 2023, this long observational tradition received new momentum with the launch of a “PRO-AM” collaboration between professional and amateur astronomers. This initiative makes use of the Solar Explorer (Sol’Ex), a compact, high-quality spectroheliograph designed by Christian Buil. The aim of the collaboration is to record solar images on a daily basis, and whenever possible several times per day. Thanks to dozens of observing stations distributed across different geographical locations, the impact of local weather conditions is significantly reduced.
Meanwhile, the range of available spectroheliographs has been further expanded. In addition to the original Sol’Ex, Sol’Ex Pro, Sol’Ex V2, Sol’Ex by James R, Sol’Ex original, and the SHG700 are now available, enabling amateurs with diverse technical backgrounds and resources to participate in the project.
In 2025, a total of 59 amateur astronomers were actively involved in the PRO-AM collaboration. The majority of them, 39 participants, were based in France, while the others were spread across nine additional countries. Together, they were responsible for no fewer than 4,548 observations in various spectral lines, including Hα, Hα 2cb, Ca II H (H3), Ca H1v, Ca II K (K3), and Ca K1v.
Thanks to the strong commitment of the amateur community, there was only a single day in 2025 without an Hα observation, namely 22 December. For Ca II H and Ca II K observations, however, the number of days without data remains significantly higher, highlighting the importance of further expanding the observing network.
Within this international collaboration, I am currently still the only Belgian amateur actively submitting images to the Meudon Observatory. In total, I submitted 82 observations in 2025, placing me seventh among the most active amateur contributors. For the specific Ca II H and Ca II K lines, I rank fourth and fifth respectively. This clearly demonstrates not only the value of individual dedication, but also the crucial role amateur astronomers play in achieving long-term, continuous solar monitoring.
