Filters
If you use a “one shot color camera” in relatively dark skies, filters aren’t essential. But even so, they’re VERY useful. Check out this image… taken with a filter, it required only 60s to capture. Getting the same color and detail without a filter might have taken 20 minutes or more, and still might not have equaled this image.
I’m lucky enough to live in Bortle 4 skies. For many city dwellers, Bortle 4 is a “dark site”, a place they travel to. It happens to be my back yard.
In light polluted skies, there’s a lot of extraneous light in wavelengths that a red pixel in my camera might respond to. Most of that light is close to, but not identical, to the wavelengths that an emission nebula like the Rosette puts out. A “light pollution filter” works by letting through only (or mostly) the natural wavelengths (H-Alpha, H-Beta and Oxygen III emission lines). The result is a huge improvement in the contrast and signal to noise ratio of the filtered images.
The same is true in less light polluted skies like mine. Light pollution doesn’t completely swamp the natural emissions, but the filters still improve the S/N ratio.
This image was taken with the Optolong L-eNhance filter. I think it works really well, but there are other good filters in the market, and some will work better than others depending on your light pollution.
Though less dramatic, UV/IR cut filters are useful when imaging most targets other than emission nebulae. The impact is more subtle, but stars and galaxies tend to appear just slightly sharper than in images taken without any filter.