Take images like Hubble
Astronomik narrowband emission line filters are perfectly matched to the requirements of astronomical Deep-Sky imaging. The three most important emission lines of Oxygen (OIII), Hydrogen (H-alpha), and Sulfur (SII) are offered in 12nm or 6nm Bandwidths (FWHM). These filters are guaranteed to have a transmission of 90%, but often are higher. Imaging with Astronomic narrowband filters can work in dark sites as well as light polluted areas. This is because they block most wavelengths where the pollution resides.