Astronomy Specialist



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The Optolong L-Pro filter is a light pollution multiband filter designed to reduce the effect of light pollution while offering a great white balance.

CLS, UHC, L-eNhance, L-eXtreme and narrowband filters are very effective in increasing the contrast of emission nebulae but they are ineffective on deep sky objects that have a continuous spectrum such as galaxies, globular clusters and reflection nebulas. The L-Pro works as a universal light pollution filter for all kinds of celestial objects as it only cuts off the main light pollution wavelengths.

  • 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 at OIII (496nm and 500nm), H-beta (486nm), NII (654nm and 658nm), H-alpha (656nm) as well as SII (672nm).
  • Five transmission bands for an optimal colour balance.
  • It can also be used for visual observations as well as for 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 anodised 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.

Optolong L-PRO

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 on CWL (central wavelength) and no deviation affected by temperature changes. The planetary rotation system offers precision and homogeneity of coatings ensuring high transmission of 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 Multibands
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, clip on Eos Full Frame (FF), clip on Nikon Full Frame (FF)


Optolong filter box

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