ZWO SII 7nm CCD Imaging Filter - 2"
Sulfur is in the deep red of the spectrum near 672 nm. When combined with H-a and OIII (Hydrogen-Alpha and Oxygen III, or double ionized oxygen) SII will produce images with colors that are reminiscent of those taken by the Hubble Space Telescope.
The ZWO SII 7nm Filter is mounted in a metal 2" cell and comes in a protective plastic case. ZWO narrowband filters are fine-optically polished to reach an accuracy of 1/4 wave. Their performance is further enhanced by multiple layers of anti-reflection coatings.