Filter,2", High Contrast

USD $90.00
2" Specialty blocking filter: transmits only 480-510nM. M28.4x0.6
2UHC is a filter that blocks the visual spectrum except for wavelengths between 480nM and 510nM. Often called a Nebular or ALP (anti-light pollution) filter, this allow passage of ionized oxygen and hydrogen lines, but blocks light pollution reflectance from mercury and sodium vapor lamps. Threads into all 2" accessories.