What is narrowband imaging all about?
This portion of Astrographica is dedicated to the pursuit of the imaging of deep sky astronomical objects with specialized “narrowband” filters. Unlike standard RGB or LRGB imaging, narrowband filters let through just a very narrow range of light, usually from 3nm to 14nm in bandpass width. In RGB colour imaging, the red, green and blue filters each cover about one third of the visual spectrum, from over 700nm (red), to under 400nm (blue). The most commonly used narrowband filters include hydrogen alpha (Ha), ionized oxygen (OIII), and sulphur (SII), although other spectral lines are occasionally used. This type of imaging has several interesting attributes. First, it allows for high-quality imaging from otherwise poor locations and times of the month. Regular light pollution, and even the presence of moonlight, has very littled effect on the wavelengths typically used. Secondly, since the other part of the “spectral continuum” is filtered out, stars tend to be smaller, and cameras do
