Optolong L-Ultimate 3 nm Dual Band Filter

It is a 3nm dual narrow band filter designed for drastically reduce the effects of light pollution. The 3nm band isolates emissions from the H-alpha (red) and OIII (green-blue) nebulae. 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 lamps and unwanted natural light caused by the emission of neutral oxygen in our atmosphere. Maximizes transmission of the nebula's main emission lines in OIII (496nm and 500nm) and H-alpha (656nm).

The advantage of the L-Ultimate filter is that it only lets through the emission lines OIII (500.7 nm) and Ha (656.3 nm). In this case, all other light pollution emission lines are eliminated, so that only the emission and reflection signals of the fog are captured during the recording. As a result, the sky background of the image is darker, and the contrast between the nebulae and the signal-to-noise ratio are greatly improved. In addition, in areas with heavy light pollution, the product can selectively filter light pollution and interference signals through the emission lines of nebulae, finally avoiding the effects of light pollution on astrophotography.

It differs from the dual narrowband filters L-eNhance and L-eXtreme in that L-Ultimate has an even narrower bandwidth that only lets through Ha and OIII emission lines. You get a darker sky background, more contrast in the image, and suppression of stars.

L-Ultimate has also been optimized in terms of halo performance, so no haloes are seen when shooting around a brighter star.

A blocking of IR/UV is integrated.