The 2" Ultra High Contrast Filter is unbeatable for revealing nebulosity. This is achieved by passing three nebula emission lines-the two doubly ionized oxygen lines (496 and 501nm) and the H-beta line (486nm) -while blocking light-pollution and Sky Glow. The result is superb views of the Orion, Lagoon, Swan and other extended nebulae. The strictest quality control standards are employed throughout the production process. Each Ultra High Contrast Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the O-III and H-beta emission lines. The way an UHC filter works is very simple.
It filters out the brightening of the sky due to artificial light. As many celestial objects, such as nebulae, radiate at other wavelengths, a considerable increase in contrast can be achieved by this. The background sky appears darker and, all at once, faint details become visible. Observing first without and then with a UHC filter makes the presence of an object very obvious. The use of an UHC filter is not only useful at light-polluted sites; the contrast is also increased at dark sky sites. Many objects only first become visible at all when using an UHC filter.
But also, highlights such as the Orion, Lagoon or Swan nebulae, show a whole new side to them. UHC filter is one of the most useful accessories you can have and no eyepiece case should be without it. The UHC filter can be used with all 2" eyepieces.