What filter(s) do you use and/or find useful for eliminating or downplaying the effects of light pollution? Let's try not to get into processing techniques, etc in this discussion as that topic can merit it's very own discussion.
I almost exclusively use the Orion Broadband Skyglow Filter. The SkyGlow Imaging filters pass most light from deep-space objects while selectively blocking unwanted light from street lights and other undesirable light sources.
This filter is useful in areas of moderate or heavy light pollution, as well as fairly dark areas that are still effected by minor light pollution. Unlike other “broadband” light pollution filters, which block large portions of the visible spectrum, the SkyGlow Imaging filter rejects only narrow regions of the spectrum associated with the wavelengths of light emitted by common outdoor lighting. As a result, the images obtained with this filter will preserve a virtually neutral color balance, while greatly improving image contrast. The filter is designed exclusively for imaging use.
The SkyGlow Imaging filters also block infrared (IR) and ultraviolet (UV) wavelength light. The filter has been designed this way in order to provide the highest transmission of visual wavelengths of light without the contaminating effects of IR and UV light which can reduce image contrast and lead to bloated star images.
Of course,with this filter, as with any other, you must set up a custom white balance frame using a gray card. Otherwise you're images will have a distinctly green hue about them...
I've have two filters that I've tried, though I need to take more images to determine which I find to be the best. The two are an Orion SkyGlow UltraBlock and a Meade Nebula filter (#911).
The Orion while doing a very good job of eliminating light pollution seems to block perhaps a bit too much of the light spectrum, while the Meade, not as good at removing the light pollution, seems to be much better at producing good color and picking up fainter detail. As soon as I get some warmer nights here I plan on do a litte more testing to see ultimately, for me, which is the better of the two.