Spectra from DIY Spectrometer comparing sky, tree trunk and CFL bulb, through Sky Watcher Evostar 72ED telescope 28/5/2019. Note that although the x-axis is the same scale for all three graphs, the y-axis scale differs.
Coma beam splitter 1.25″.
Ocean Optics collimating lens at telescope end of fibre optic where enters beam splitter.
I can’t see any meaningful difference between sky and tree trunk spectra but the CFL bulb clearly different.