ZWO 36mm OIII 7 nm Filter
ZWO’s 36mm doubly ionized oxygen (OIII) filter, is one of the most popular narrowband imaging filters. In fact, when used with an H-Alpha and SII filter, your images will have enhanced coloring like images taken by the Hubble Space Telescope. Planetary nebulae and supernova remnants emit most of their light in the OIII line, which is light in the blue/green, or teal portion of the spectrum near 500 nm.
The ZWO OIII 7nm 36mm Filter is unmounted. 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.