The Optolong CLS broadband filter is designed to improve the visibility of various deep-sky objects by selectively reducing the transmission of wavelengths of light pollutants, specifically those produced by artificial lighting including mercury vapor lamps, both high & low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). The filter is highly transparent in the main nebula emission lines at OIII(496nm and 500nm), H-beta (486nm), NII(654nm and 658nm), H-alpha(656nm) as well as SII(672nm). It's suitable for enhancing the contrast and details in light-polluted areas.
Main Use and Performance
The CLS filter is different from the CLS-CCD filter - the CLS-CCD comes with an infrared wavelength 700-1100nm cut-off, which is helpful in use with color CCD cameras and modified DSLRs for astrophotography. For visual use, the CLS filters are appropriate.
It works well on most emission nebulae, planetary nebulae and supernova remnants.
You will see a noticeable boost in contrast and visibility of the fainter outer nebulae detail.
Note that light pollution filters do not eliminate the effects of light pollution or increase the object's brightness. In many cases they instead increase the contrast between nebula and night sky.
WARNING: This filter is not designed for sun observation