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CLS filters are broadband filters, which means they allow wide incident light wavelength ranges to pass through. They block light only in selected sections of the spectrum. These blocked sections are chosen in such a way that they coincide with the emissions from artificial light sources. In addition to artificial sources, there are also natural sky brightness phenomena, which are also blocked by CLS filters. Ultimately, the sky background appears darker with a CLS filter. The object being observed stands out more clearly against the background.

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Omegon Filters Pro 2'' CLS filter
Omegon
Filters Pro 2'' CLS filter
$ 99.00
ready for shipping in 24 h
Omegon Filters Nebula/ city light filter 1.25 ''
Omegon
Filters Nebula/ city light filter 1.25 ''
( 3.5 / 5 )
$ 39.90
ready for shipping in 24 h
Omegon Filters Light Pollution Filter, 2”
Omegon
Filters Light Pollution Filter, 2”
( 3.33 / 5 )
$ 59.00
ready for shipping in 24 h
Omegon Filters Pro Nebula CLS Deep Sky Filter 1,25''
Omegon
Filters Pro Nebula CLS Deep Sky Filter 1,25''
$ 69.00
ready for shipping in 24 h
Omegon Filters 1.25'' deep sky filter
Omegon
Filters 1.25'' deep sky filter
$ 89.00
ready for shipping in 24 h
Omegon Filters 1.25'' Clear Sky filter
Omegon
Filters 1.25'' Clear Sky filter
$ 129.00
ready for shipping in 24 h
Optolong Filters Clear Sky Filter 82mm
Optolong
Filters Clear Sky Filter 82mm
$ 237.00
ready for shipping in 24 h
Optolong Filters Filter L-eNhance 1.25
Optolong
Filters Filter L-eNhance 1.25
Our price:
RRP:  $ 205.00
$ 190.00
ready for shipping in 24 h
Optolong Filters Clear Sky Filter 77mm
Optolong
Filters Clear Sky Filter 77mm
$ 183.00
ready for shipping in 24 h
STC Filters Astro Multispectra Filter 2"
STC
Filters Astro Multispectra Filter 2"
$ 378.00
ready for shipping in 24 h
Chroma Filters LoGlow Light Pollution 1.25"
Chroma
Filters LoGlow Light Pollution 1.25"
$ 540.00
ready for shipping in 3-5 weeks
Chroma Filters LoGlow Light Pollution 2"
Chroma
Filters LoGlow Light Pollution 2"
$ 960.00
ready for shipping in 24 h
Astronomik Filters CLS Clip Nikon Z XL
Astronomik
Filters CLS Clip Nikon Z XL
$ 216.00
ready for shipping in 3-7 days
IDAS Filters Night Glow Suppression Canon EOS APS-C
IDAS
Filters Night Glow Suppression Canon EOS APS-C
Our price:
RRP:  $ 389.00
$ 356.00
ready for shipping in 3-5 weeks
Astronomik Filters CLS CCD 50mm
Astronomik
Filters CLS CCD 50mm
$ 248.00
ready for shipping in 3-7 days
Astronomik Filters CLC Canon EOS clip filter APS-C
Astronomik
Filters CLC Canon EOS clip filter APS-C
$ 140.00
ready for shipping in 3-7 days
Optolong Filters L-Ultimate 2"
Optolong
Filters L-Ultimate 2"
Our price:
RRP:  $ 432.00
$ 417.00
ready for shipping in 24 h
Explore Scientific Filters 2" CLS filter
Explore Scientific
Filters 2" CLS filter
Our price:
RRP:  $ 90.00
$ 62.00
ready for shipping in 1-2 weeks
Astronomik Filters CLS Sony Alpha Clip filter
Astronomik
Filters CLS Sony Alpha Clip filter
$ 216.00
ready for shipping in 24 h
Explore Scientific Filters 1.25" CLS filter
Explore Scientific
Filters 1.25" CLS filter
Our price:
RRP:  $ 63.00
$ 43.90
ready for shipping in 1-2 weeks
Astronomik Filters CLS XT Clip Canon EOS APS-C
Astronomik
Filters CLS XT Clip Canon EOS APS-C
$ 162.00
ready for shipping in 3-7 days
Vaonis Filters CLS Filter for VESPERA
Vaonis
Filters CLS Filter for VESPERA
$ 248.00
ready for shipping in 3-5 weeks
Astronomik Filters CLS CCD EOS clip filter
Astronomik
Filters CLS CCD EOS clip filter
$ 172.00
ready for shipping in 3-7 days
Astronomik Filters 2" CLS CCD filter
Astronomik
Filters 2" CLS CCD filter
$ 248.00
ready for shipping in 24 h
Astronomik Filters CLS Clip Pentax K
Astronomik
Filters CLS Clip Pentax K
$ 216.00
ready for shipping in 24 h
Optolong Filters L-Pro Filter 77mm
Optolong
Filters L-Pro Filter 77mm
Our price:
RRP:  $ 389.00
$ 311.00
ready for shipping in 24 h
Optolong Filters L-Ultimate 1,25"
Optolong
Filters L-Ultimate 1,25"
$ 280.00
ready for shipping in 24 h
Optolong Filters L-Pro Clip Sony Full Frame V2
Optolong
Filters L-Pro Clip Sony Full Frame V2
$ 259.00
ready for shipping in 24 h
Optolong Filters L-Quad Enhance 2"
Optolong
Filters L-Quad Enhance 2"
$ 259.00
ready for shipping in 3-5 weeks
Astronomik Filters CLS CCD XL Clip Canon EOS R
Astronomik
Filters CLS CCD XL Clip Canon EOS R
$ 270.00
ready for shipping in 3-7 days
Astronomik Filters CLS XL Clip Canon EOS R
Astronomik
Filters CLS XL Clip Canon EOS R
$ 216.00
ready for shipping in 3-7 days
Astronomik Filters CLS CCD Clip Nikon XL
Astronomik
Filters CLS CCD Clip Nikon XL
$ 259.00
ready for shipping in 3-7 days
Astronomik Filters CLS M52
Astronomik
Filters CLS M52
$ 205.00
ready for shipping in 3-7 days
Astronomik Filters CLS CCD Sony Alpha Clip filter
Astronomik
Filters CLS CCD Sony Alpha Clip filter
$ 259.00
ready for shipping in 3-7 days
Astronomik Filters CLS Nikon XL Clip
Astronomik
Filters CLS Nikon XL Clip
$ 216.00
ready for shipping in 3-7 days
Astronomik Filters CLS CCD EOS M Clip filter
Astronomik
Filters CLS CCD EOS M Clip filter
$ 172.00
ready for shipping in 24 h

The figure below illustrates the principle using the example of the NGS1 filter from IDAS. The black transmission curve shows which wavelength ranges the filter allows to pass through. 100% would mean no filter effect at all. The transmission curve also shows which light wavelength ranges are blocked by the filter. These ranges are associated with the emissions from sodium-vapour lamps and other disruptive light sources. The CLS filter filters out this unwanted light.

The CLS filter allows broad ranges to pass through and is therefore also suitable for small optics.

CLS Transmissionskurve