Quote Originally Posted by Photo Engineer View Post
This harmonic vanishes with a UV filter and is one of the faults of these particular instruments.
It's not really a fault, it's just a function of using a diffraction grating. A spectometer using a prism will not have this issue. Prisms have their own issues...

I bought a 4 inch spherical mirror with a diffraction grating on it to make one of these. Someday I'll do it!

Colored LEDs should be an easy way to calibrate any spectrosensitizer now that red, green, blue and even UV LEDs are readily available.