Alpine Astronomical Baader 4.5nm Sulfur-II Ultra-Narrowband CCD Filter (2" Eyepiece Filter)

Centered on the 673nm wavelength and passing an extremely narrow bandwidth, the 2" 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.