The Omegon OIII filter is comparable to the Omegon UHC filter in its function. The difference is that this filter only allows the light of doubly ionized oxygen through. This means that there is an enormous increase in contrast with diffuse, planetary and extremely dim nebulae. This is a special narrowband filter which allows an even smaller range of wavelengths than the Omegon UHC filter. Even so, there are innumerable astronomical objects which can be first observed in detail with this filter or cannot be seen at all without it. A prime example is the Veil nebula in the constellation of Cygnus.  An Omegon OIII filter is not only useful at light-polluted sites; the contrast is also increased at dark sky sites. The Omegon OIII filter can be used with all 1.25” eyepieces.