The Optolong L-Ultimate 3nm dual band filter is designed to drastically reduce the effects of light pollution. The 3nm isolates the nebulae's emissions into H-Alpha (red) and OIII (green-blue). It blocks light pollution, maximizes the signal from nebulae, and darkens the sky background. It also blocks artificial light from mercury vapor lamps, high and low pressure sodium vapor lights, and unwanted natural light caused by the emission of neutral oxygen in our atmosphere. Maximizes the transmission of the main emission lines of the nebula in OIII (496nm and 500nm) and H-alpha (656nm). Used with DSLR, color/MONO CMOS and CCD, however, this filter is not suitable for fast ratio systems. The advantage of the 2" L-Ultimate Filter is that it only passes through OIII(500.7nm) and Ha(656.3nm) emission lines, and all other light pollution emission lines are eliminated so that only the emission and reflection signals of the nebula are captured during imaging. Therefore, the sky background of the image is darker, and the contrast between the nebulae and the signal-to-noise ratio are improved to the greatest extent. In heavily light pollution areas, the L-Ultimate filter can also selectively filter light pollution and clutter signals through the emission lines of nebulae, and finally avoid the impact of light pollution on astrophotography. Substrate: Optical Glass FWHM: OIII 3nm, Ha 3 nm Blocking Range: 300 nm - 1000 nm Blocking: >OD4 Surface Quality: 60.40 Transmitted Wavefront RMS: 4 Parallelism: 30 s
