I finally bought the book "Guide de l'observation solaire avec un spectrohéliographe" by Christian Buil and Valerie Desnoux, subtitled "Explorer le Soleil invisible avec Sol'Ex".
There’s just one major catch... it’s written entirely in French, and there’s no sign of an English translation anywhere on the horizon. Since my French is pretty rusty, this is going to be a real challenge—but exploring the 'invisible Sun' with the Sol'Ex will be well worth the effort!
