I once looked at Betelgeuse through my Dob with a diffraction grating between the eyepiece and my eye. I saw many absorption bands, especially at longer wavelengths.Tried the same with Rigel and Sirius but neither was as spectacular as Betelgeuse.

Out of curiosity, what does the spectrum of a nebula look like using your prism setup? I imagine there must be some neat looking identifying characteristics?