ZWO 1.25″ SII 7 nm Filter
The ZWO SII 7nm Filter is mounted in a metal 1.25″ 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.
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.