"What I'm actually going to do is use Silent Image to create illusions of spectroscopy stations for everyone. If a Silent Image of a mirror works as a mirror, a Silent Image of a spectroscope should work as a spectroscope, or so I reason. If an illusionary mirror works as a mirror, a light-exclusion hood should work as a hood, a light source should work as a light source, and a prism should work as a prism."
"I'll also create illusions of prisms the correct size and shape to do the job, illusions of evenly frequency-distributed light that's good for testing absorption lines, and illusions of diffraction gratings."
"I'm going to maintain my concentration on that for as long as I can, and, before the spell ends, you need to manage to either Prestidigitate quartz to clarity, or prestidigitate a surface to behave like a diffraction grating. If possible, also Prestidigitate a light source to behave like an evenly-frequency-distributed light source, but that may legit be harder."
"And if we can't get that done today - take note of how far you got in deliberately shifting the frequency lines, where you started, where you ended up, and how much progress you made."
"Assuming, of course, that this whole clever plan does not completely utterly fail on step zero."
"Carissa, you said you had an illusion spell prepped, right? You're on learning to make your own illusionary spectroscopes that work, in case we're stuck with illusionary spectroscopes for a while, so that I'm not the only one who can cast them using my one first-circle wizard spell per day. I mean, fine if you can teach others here after that, but you being able to learn it yourself would give us some breathing room. You have good concentration."