Solar Prominence Emissions

During a recent Zoom session with the Leeds AS, there was discussion as to how the early photographs of solar prominences were obtained at total eclipses, when the “red (or pink) flames” apparently successfully registered on plates supposedly not sensitive to red light.

We provisionally concluded that the emissions from H-beta, He and CaK in the shorter end of the spectrum actually provided the “actinic” components for the photographs.

Can anyone put me onto a typical prominence spectrum which shows the relative flux of these components as compared to H-alpha emission?

And/or a better explanation?

Thanks!