It's a broadband filter, and time has, unfortunately, made these far less effective at reducing light pollution.
A recent measurement of the light in the sky of Los Angeles found over 600 different spectral lines of LP in the sky:
mercury vapor, high pressure sodium vapor, low pressure sodium vapor, high temperature LEDs, low temperature LEDs,
LCD billboards (the worst!), fluorescent bults, incandescent bulbs, halogen bulbs, etc. (even aurorae and oxygen glow).
Back when almost all LP was incandescents and mercury vapor, it was easy to put a notch in the spectrum and reduce the LP.
Today, the effectiveness of these LPR or broadband filters is reduced to being photographic accessories for already quite-dark sites.
Very narrow filters are necessary for viewing nebulae in urban environments (e.g. H-ß, O-III, UHC) or for imaging (H-α, S-II, N-II, O-III all with extremely narrow bandwidths)
With the nature of modern light pollution, the older LPR filters may actually make matters worse by scattering light of wavelengths passed through.
I'd save the filter for dark skies and use narrower filters for viewing nebulae in an LP environment.
[I've used a narrow UHC filter in skies where the naked eye limit was 2 to 2.5, and the sky was blue (!) at night, and the filter worked decently on some of the brighter nebulae.]
Edited by Starman1, 13 February 2018 - 06:04 PM.