[avandonk]

Here is a composite of various spectra.Two streetlamps, Mercury and High Pressure Sodium.
A Tungsten lamp.
Also the light passed from a Tungsten lamp by two light pollution reduction filters ,a nebula filter and a red filter with a cut at 640 nM
These were made with a clear CD you get with a pack of 50.They make quite reasonable diffraction gratings.

From the top

Kenko R64
Nebula Filter NBN-PV from Hutech
LPR from Roger at BATSC
LPS-P2 from Hutech
Mercury street lamp
High pressure Sodium street lamp
Tungsten light globe

I wanted a visual way to see exactly what these filters did and how they related to those
light polluting lamps.As you can see High Pressure Sodium is the difficult one.