#VoxxedDaysCERN26

The Sol'Ex (aka "Solar Explorer") is a DIY instrument invented by Christian Buil, which enables observations of the sun in different wavelengths which has revolutionized full solar disk imaging in amateur astrophotography. It is a kind of so-called "spectroheliograph", an instrument which was invented back in 1890. With modern technologies like CMOS cameras, we can now build cheap devices which makes observing the sun accessible to everyone. What is interesting, however, is that such a device doesn't directly produce an image: software processing is mandatory, because we need to reconstruct an image from a video which only contains images of a portion of the light spectrum.
With Sol'Ex, this processing was done with INTI, a program written in Python by Valérie Desnoux. As an amateur astronomer, I have used software for astronomy image processing, but as a developer, I hadn't implemented anything myself yet. Therefore I challenged myself and started a project in order to write my own software, called JSol'Ex, in Java. This project started as an experiment, so that I understand the "science" behind the image reconstruction, and see if I was still capable, after 20+ years of programming, to implement algorithms based on research papers. In this session, I will explain what I have learnt: the principles of capturing images with the Sol'Ex instrument, how images are reconstructed, but also the various features I have added to JSol'Ex which make it now a reference in its domain.

Devoxx

Cédric Champeau, an Oracle/Micronaut developer, presents JSol'Ex, a Java-based open source application he built as a personal project to process solar spectroheliograph data. The tool reconstructs solar images from raw video scans captured through a DIY spectrograph device, enabling amateur astronomers to produce H-alpha, calcium, sodium, and helium images, Doppler velocity maps, eruption detection, and differential rotation measurements. The tech stack includes modern Java features (Vector API), GraalVM for native image generation, Gradle, and LWJGL for GPU acceleration via OpenCL. The talk includes a live demo showing image reconstruction, scripting capabilities, 3D spectral cube visualization, spherical tomography, and Ellerman bomb detection — phenomena previously accessible only to professionals.

JSol'Ex: solar image processing in Java by Cédric Champeau