ZWO 2" 7nm Narrowband S-II Filter

The ZWO narrowband S-II 7nm filter passes light at 672nm wavelength with a bandpass of 7nm which is designed for nebula observation. It is suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants, use it with H-alpha and OIII narrowband filters (SHO Set) for tricolor CCD astrophotography. (H-alpha and OIII Filter Sold Separately).

Narrowband filter does not eliminate the effects of light pollution or increase the object's brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.

It can reduce the transmission of certain wavelengths of light, specifically, those produced by artificial light including mercury vapor, and both high and low-pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).