This prevents me to use them, as calibrating a spectrometer is very hard. almost like piano tuning, and requires special technicians...
Who said it is hard? For Little Garden it is as easy as finding a couple of reference peaks from a familiar light source like a CFL and adjusting them to their proper wavelengths, just to align spectrometer scale to the exact wavelengths. A 5 minutes job.
You likely can't calibrate amplitudes (=powers) properly at all on any webcam spectrometer of such class, so no reliable CCT/CRI no matter how hard you try, but yeah you'll still have a heck of fun with hi-res spectrums for $60 spent!
