Nicolas Lefaudeux

Overcoming the Challenges of Total Solar Eclipse Imaging: Dynamic Range, Signal-to-Noise Ratio, and Resolution

Abstract

Total solar eclipses are rare, brief events with no opportunity for repeat observations, making it impossible to test configurations in real conditions or compare results across different settings. This constraint necessitates thorough pre-eclipse analysis to define the optimal imaging setup.

Capturing the solar corona presents additional challenges due to its extreme dynamic range, low-contrast structures, and details spanning from large to fine-scale features. Unlike most astronomical imaging, where faint objects and low photon counts are primary challenges, eclipse imaging deals with a bright target, leading to different limitations and specific constraints. Achieving a high signal-to-noise ratio (SNR) and resolution is essential to reveal the intricate details of the solar corona.

This presentation examines the factors affecting signal quality at three critical stages: acquisition, calibration, and post-processing. We explore the trade-offs involved in optimizing image quality for both high-resolution and large field-of-view imaging. Finally, we showcase examples of eclipse images and data, demonstrating their potential for revealing hidden details and structures in the solar corona.

Bio

 I am a French optical engineer and amateur astrophotographer with a deep passion for physics and optics. My interest in astronomy began at the age of 12 when I received my first telescope, a 115/900 Newtonian reflector. By 16, I had crafted my own 260mm Dobsonian telescope, hand-polishing the primary mirror and constructing the entire setup from plywood and salvaged parts. Around that time, I started astrophotography using a vintage Zenit camera.After two years of studying mathematics and general physics, I specialized in optics and related disciplines, including sensors and image processing, during a three-year program at the "Institut d’Optique", where I graduated in 2006. Since then, I’ve worked as an optical engineer on a diverse range of topics such as polarization imaging, optical metrology, adaptive optics, and high-resolution biomedical imaging. My core expertise lies in optical design and image processing.

The 2017 Total Solar Eclipse marked a significant milestone in my astrophotography work. I dedicated hundreds of hours to planning and refining my approach: optimizing my telescope for contrast, designing custom 3D-printed components for automation, rehearsing extensively, and developing algorithms to produce high-quality HDR composites.

This project ignited my interest in Solar Eclipses, and I’ve since continued to improve my equipment, image acquisition, and post-processing to push the boundaries of solar eclipse photography.