Specifically designed for use on fast astrographs to eliminate the light loss commonly experienced with conventional filters, the 2" eyepiece filter-threaded Alpine Astronomical Baader Oxygen-III 4.5nm Ultra Narrowband CCD Filter works best during astrophotography and astroimaging with optical systems from f/8 to f/3. Its narrow 4.5nm bandpass selectively isolates just two ionized oxygen lines, blocking all others, allowing you to capture the tight emission line regardless of the moon phase and light pollution—improving the contrast of diffuse, planetary, and extremely faint nebulae when imaged against the stark black backdrop of space.
Planeoptically polished, dielectric anti-reflection coated, and IR blocked, the filter uniformly passes the maximum amount of bandwidth possible to virtually eliminate halos, reflections, and ghosting. The filter is mounted in an aluminum frame that has been threaded to fit standard 2" eyepieces and accessories for projection and afocal imaging techniques. When stacking and processing images using the other two most popular wavelengths of H-alpha and Sulfur-II, users are able to concentrate on three distinct colors to produce brilliant composite images of a wide array of astronomical objects, including nebulae and planets.
This filter is intended only for deep-sky astroimaging with CCD systems, and should never be used for direct solar viewing or solar photography as permanent injury to your eye and equipment can occur, up to and including blindness.