The ZWO 36mm SII Filter - 7nm:
This SII Narrowband filter transmits only Sulfur-ii wavelength light, which is found in most nebulae, star clusters, galaxies, and stars, making these filters ideal for complex false color imaging of such regions.
SII filters such as this are excellent for boosting contrast and are most definitely a must-have for imaging in areas with high levels of light pollution.
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. Additionally, you can use it with H-alpha and OIII narrowband filters (SHO Set) for tricolor CCD astrophotography.
Both of the new SII and Ha filters from ZWO have a positive and negative side. Telling the camera and telescope sides is very simple. Let the image below show you how!