We all know that filters, especially narrowband, make a huge difference when used at light polluted sites. This gallery illustrates their utility at sites with varying levels of light pollution. Depending on the level of light pollution, an LPS that tries to preserve colour balance can be very ineffective, but a duo-band (two fairly narrow passbands) can make an obvious difference. The higher the light pollution, the narrower the passband(s) we should employ. But do not discount using filters at even very dark sites, like in the first slide below.
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