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Narrowband filter achieve contrast enhancement in emission nebulae only in that they only one member of the wavelength range of the light to the spectral lines of hydrogen (Ha, 656nm), oxygen (O III, 501 nm), sulfur (SII, 672nm), and so on therethrough. The filters can always be used for photography, even when the moon is in the sky, or as a filter against the light pollution in a big city. The length of the exposure time does not matter - even long-time photography can be made.

The narrow-band range of wavelengths is referred to as FWHM (at Engl. Full-width half-maximum intensity) are defined. Narrowband filters reduce the background noise. Therefore, narrow-band filter in the production are much more difficult and expensive, since does not have to be taken only on the wavelength range, but also on the passage in this small wavelength range here. The most difficult thing in achieving a high passage for only a very small wavelength range. For example, if would decrease the transmission curve, the signal for the wavelength range would be reduced and the gain for the S / N (signal to noise ratio) would no longer be achieved.