ZWO Narrowband 1.25" filter set
ZWO OIII 1.25" Mounted Filter
OIII, or doubly ionized oxygen, emits light in the blue/green, or teal portion of the spectrum near 500 nm. Planetary nebulae and supernova remnants emit most of their light in the OIII line.
ZWO H-a 1.25" Mounted Filter
Hydrogen-Alpha is the most dominant emission line in star-forming regions. H-Alpha light is created by atomic hydrogen, and is responsible for the red color seen in most nebulae. The Ha portion of the spectrum is at 656 nm.
ZWO SII 1.25" Mounted Filter
Sulfur is in the deep red of the spectrum near 672 nm. When combined with H-a and OIII, these three filters will produce images with colors that are reminiscent of those taken by the Hubble Space Telescope.
These ZWO 1.25" filters are mounted in a metal cell and come in a plastic storage box. ZWO narrowband filters are fine-optically polished to reach an accuracy of 1/4 wave, and they are capable of light transmission up to 80%. Their performance is further enhanced by multiple layers of anti-reflection coatings.