Astronomy Specialist


$159.00 AUD
SKU: OP-11901




The Optolong CLS-CCD (City Light Suppression) broadband filter is designed to improve the visibility of emission deep sky objects.

Different from the Optolong CLS filter, the Optolong CLS-CCD cuts off the infrared radiation between 700-1100nm (IR/UV Cut).  It works with astronomy cameras and modified DSLR's for astrophotography. 

It selectively reduces the transmission of wavelengths of artificial light, specifically those produced by mercury vapour lamps, both high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). The high transmission 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) enhances the contrast and details for both visual and photographic purposes in sub-rural areas. Compared to the UHC filter, the CLS has a wider bandpass so it is preferred in areas with mild to moderate light pollution. 

  • It blocks the artificial light from mercury vapour lamps, both high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).
  • Maximum transmission of the main nebula emission lines: OIII (496nm and 500nm), H-beta (486nm), NII (654nm and 658nm), H-alpha (656nm) as well as SII (672nm),
  • It can also be used for visual observations as well as in astrophotography.
  • Ideal for sub-rural areas with moderate light pollution.
  • It incorporates an IR/UV-Cut filter that is necessary in astrophotography, especially for astronomy cameras that are sensitive to the infrared radiation.
  • Ultra-thin filter cell to maximise the compatibility with most filter wheels.
  • Multi-layers anti-reflection coating.
  • Cell in Aerometal Material, CNC machined, sand blasted, black anodized and laser engraved.
  • Plastic PP Case, high pressure EVA Case Lining.

Light pollution filters do not eliminate the effects of light pollution or increase the object's brightness. It does increase the contrast between nebulae and night sky.


The interferential coating is deposited on the substrate using electron-beam gun evaporation with ion-assisted deposition coating technology. This increases the filter durability and resistance to scratching, as well as stability of the CWL (central wavelength). The planetary rotation system offers precision and homogeneity of the coatings ensuring high transmission of the pass-band and high optical density off-band.

WARNING: Optolong filters are not designed for sun observations. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTERS. You could become BLIND if you fail to observe the warning.

Passing band Broadband
Glass thickness

2.0 mm (for 1.25" and 2" filters) ; 1 mm (clip series)

Optical flatness

1/4 λ (wavefront)

Band-pass transmission 90% across major nebulae bandpass
Coating Fully multi-coated
Surface quality
60/40 (in accordance with US military watch MIL-O-13830)
Parallelism 30"
Glass type
Schott monolithic optical substrate (non glued)
Available sizes 1.25", 2", clip on EOS-C. 

Optolong filter box


    Customer Reviews

    Based on 1 review
    peter martin

    I'm bortle 4 with a stock dslr and this filter works a treat.



    From $159.00 AUD


    • 1.25"
    • 2"
    • EOS C

    Optical design

    Image circle

    Focal ratio


    Focal length

    Optical thickness



    Colour or Mono

    Pixel size

    Sensor dimensions


    Sensor diagonal

    Quantum efficiency

    Read noise

    Fullwell capacity

    Bit depth


    Camera backfocus

    Filter size

    1.25", 2", EOS C

    Filter size

    1.25", 2", EOS C

    Bandpass (FWHM)

    Bandpass (FWHM)

    Glass thickness

    2 mm, 1 mm

    Mount type

    Payload capacity

    Latitude range

    Dovetail saddle

    Slew speed


    Periodic error correction

    Counterweight shaft

    Azimuth adjustment range

    Internal diameter

    Illuminated diameter

    Compatible telescope external diameter





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