Optolong CLS Clip-On Filter

Optolong CLS (City Light Suppression) is a dual-bandpass filter which selectively enhances emission from nebulas and suppresses the transmission of light pollution sources. CLS enhances the contrast of nebulas and reduce background brightness mostly dominated by light pollution. It has wider passband than UHC (Ultra High Contrast) and thus it enhances deep sky objects under mild to moderate light pollution yet offering a more balanced colour rendition.

CLS selectively cuts out light pollution emission. For example, mercury vapor lamps, high and low pressure sodium vapor lights and skyglow caused by emission from neutral oxygen in our atmosphere. Among the emission lines enhanced are OIII (496, 500nm), H-beta (486nm), NII (654, 658nm), H-alpha (656nm) and SII (672nm).  

Highlights

• 95% transmission at major nebula emission lines
• 0.1% transmission* at off-band at Na (589nm), Hg (435nm, 578nm). 
• Multi-layers anti-reflection coating
• Precise and sharp roll-off at light pollutant lines
• 2 mm filter thickness (1.25", 2" and 77mm) | 1mm (clip series)
• Made on Schott substrate
• Finely polished to 1/4 wave accuracy
• Surface quality: 60/40 (MIL-O-13830 standard)

*equivalent to OD3 

  Recommended applications

• Canon ESO DSLR camera
• Deep sky colour imaging, particularly emission nebula or DSO emitting in the H-alpha, H-beta, O-III and S-II lines