Centered on the 673nm wavelength and passing an extremely narrow bandwidth, the 1.25" filter-threaded eyepiece Alpine Astronomical Baader 4.5nm Sulfur-II Ultra-Narrowband CCD Filter is ideally suited for use with full-frame CCD and CMOS imaging sensors on fast optical systems from f/8 to f/3 to produce high-contrast deep-sky images with short exposure times.
Its narrow 4.5nm bandpass selectively isolates the S-II wavelength, blocking all others, allowing you to capture the tight emission line regardless of the moon phase and light pollution. Planeoptically polished and dielectric anti-reflection coated, the filter maximizes light transmission uniformly to virtually eliminate distortion and halos, while blocking IR radiation that can cause ghosting when using imaging sensors that are sensitive to those wavelengths.
When stacking multiple images using the other two most popular wavelengths of H-alpha and Oxygen-III, users are able to concentrate on three distinct colors to produce brilliant composite images of the sun, nebulae, planets, and other astronomical objects. The filter is mounted in an aluminum frame that has been threaded to fit standard 1.25" eyepieces and accessories for projection and afocal imaging techniques.
This filter is specifically designed for use on imaging cameras and is not safe or intended for direct solar viewing. Using this filter for direct solar viewing can result in serious eye injury, up to and including blindness.