The light has to cover the full spectrum from red to blue for absorption lines to be noticeable, but they can determine whether light has that property by shining it through the spectroscope.

...of course that's assuming magical light behaves the same way as regular light at all, but if it doesn't, they can use mundane fire.

Also dath ilan has specialized burners that generate less light-noise when you put materials in them to burn under a spectroscope - less light from the fire and more light from the burning material; probably something about the fuel.  If they know of magical fire sources that burn with less luminous flame, that's potentially useful for spectroscopy.

Project Lawful is getting to the point where they could use an expert alchemist on staff to answer questions, or an early-professional alchemist if a real expert would be too expensive...

Uh, Keltham may possibly have been something of an idiot here, is it perhaps the case that an expert alchemist in Golarion does not cost the same amount per week as ten Security wizards?

The light has to cover the full spectrum from red to blue for absorption lines to be noticeable, but they can determine whether light has that property by shining it through the spectroscope.

...of course that's assuming magical light behaves the same way as regular light at all, but if it doesn't, they can use mundane fire.

Also dath ilan has specialized burners that generate less light-noise when you put materials in them to burn under a spectroscope - less light from the fire and more light from the burning material; probably something about the fuel.  If they know of magical fire sources that burn with less luminous flame, that's potentially useful for spectroscopy.

In related thoughts, they seem to be making progress here and spending multiple days on this stuff.  Project Lawful is getting to the point where they could use an expert alchemist on call to answer pure alchemy questions, even if they're not Lawful and not able to mentally organize the research.  Or an early-professional alchemist if a real expert would be too expensive...

Uh, Keltham may possibly have been something of an idiot here, is it perhaps the case that an expert alchemist in Golarion does not cost the same amount per week as ten Security wizards?