The Astronomik CLS filter is designed for visual observation and photography of nebulae, galaxies, and star clusters using telescopes and lenses. It completely blocks the emission lines from high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps, the majority of emissions from LED lamps as well as all lines of natural airglow while allowing the majority of visible light and nebulae emissions to pass through. This enhances the contrast between deep-sky objects and the night sky, making it ideal for photography and observation in light-polluted areas.Due to its wide passband, the Astronomik CLS filter passes a substantial amount of light, minimally dimming stars. The filter is designed to block as much unwanted light as possible while still transmitting the maximum amount of light from astronomical objects.20s exposures with JPEG data directly from the camera without further processing. Second image taken with the Astronomik CLS filter. (Canon EOS 6D astro-modified, ISO 6400, Canon EF24-105mm f/4L IS II USM @ 24mm / f/4)Other usesThe 1.25" and 2" socket models can be used for observations from light-polluted areas.AlternativesIf there is no built-in IR cut filter in your camera, a Astronomik CLS CCD filter is required.Suitability of the Astronomik CLS filtersCMOS and CCD photography: Good, requires an additional Astronomik IR-Block filterDSLR photography (original): Good, color balance is shifted but contrast is enhancedDSLR photography (astro-modified): Very good, color balance is close to perfectDSLR photography (MC-modified): Good, requires an additional Astronomik IR-Block filterGallery of images taken with our Astronomik CLS CCD filter (using the Astronomik CLS filter with a respective camera will result in identical images) Technical Data92% transmission at 486nm (H-beta)92% transmission at 496nm (OIII)92% transmission at 501nm (OIII)97% transmission at 656nm (H-alpha)Transmission range: 450 to 540nm and above 650nm Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)Finely polished optical glass, free of any striae, residual stresses, and bubblesExtremely scratch-resistant and durable coatingCompletely resistant against high humidity and aging effectsAstronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)Parfocal with other Astronomik filtersDiffraction-limitedOptimized spectral windowsDelivered in a high-quality, long-lasting filter boxDue to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.

The Astronomik H-beta filter is specifically designed for visual observation, particularly effective with larger aperture instruments. It allows the H-beta emission line to pass almost unobstructed while blocking the rest of the spectral range. This filter significantly enhances contrast, making observation of objects like the Horse Head Nebula feasible with telescope apertures ranging from 10" (250mm) to 12" (300mm).For optimal use, the Astronomik H-beta filter is recommended for aperture ratios between 1:4.5 and 1:6.The filter is most effective when used with telescopes of 8" (200mm) or larger, ensuring sufficient light gathering. Its high optical quality ensures that stars remain sharp, comparable to observation without any filter.The Astronomik H-beta filter excels in enhancing the contrast between hydrogen nebulae and the sky background, crucial for visual observation even from dark sky areas. It allows for the observation of low-contrast hydrogen regions that are nearly imperceptible without filters.Overall, the Astronomik H-beta filter is a crucial tool for deep-sky observers seeking to explore the depths of H-beta emission regions.Suitability of the Astronomik H-beta filtersVisual observation (dark skies): Very good, but only suitable for a few observation objectsVisual observation (urban skies): UnsuitableTechnical data Typical transmission of 97% transmission at 486nm (H-beta)Transmission range: 480nm to 492nmFull-Width-Half Maximum (FWHM): 12nm  Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)Finely polished optical glass, free of any striae, residual stresses, and bubblesExtremely scratch-resistant and durable coatingCompletely resistant against high humidity and aging effectsAstronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)Parfocal with other Astronomik filtersDiffraction-limitedOptimized spectral windowsDelivered in a high-quality, long-lasting filter boxDue to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.

The Astronomik OIII visual filter is tailored for observation of OIII regions, particularly effective in both light-polluted or dark sky areas. It significantly enhances the contrast between objects emitting light at the OIII emission lines and the sky background.Specifically designed for gaseous and planetary nebulae, the Astronomik OIII visual filter features a narrow pass band for both OIII lines, ensuring substantial contrast gains even under optimal observation conditions. This attribute makes a critical difference in detecting faint supernova remnants and planetary nebulae, often revealing details that might otherwise be imperceptible.The filter's application spans aperture ratios from 1:3.5 to 1:15, most suitable for telescopes starting at 6" (150mm) aperture.The filter blocks emission lines from both high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps and natural airglow, while allowing the OIII lines to pass through with high transmission. This selective filtering enhances the contrast between the celestial object and the sky background, crucial for all visual observations.Overall, the Astronomik OIII visual filter excels in enhancing the visibility and detail of OIII emission regions. It is an indispensable tool for astronomers aiming to maximize the observational potential of gaseous and planetary nebulae.Suitability of the Astronomik OIII visual filtersVisual observation (dark skies): Very good, huge contrast enhancement for OIII-emission nebulaeVisual observation (urban skies): Very good, huge contrast enhancement for OIII-emission nebulaeTechnical dataTypical transmission of 95% at 496nm (OIII)Typical transmission of 95% at 501nm (OIII)Transmission range: 494nm to 506nmFull-Width-Half Maximum (FWHM): 12nm Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)Finely polished optical glass, free of any striae, residual stresses, and bubblesExtremely scratch-resistant and durable coatingCompletely resistant against high humidity and aging effectsAstronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)Parfocal with other Astronomik filtersDiffraction-limitedOptimized spectral windowsDelivered in a high-quality, long-lasting filter boxDue to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios. Customer opinionJohn C.: »I bought your 2'' visual OIII filter from OPT and found it superior to the others I have tried. No red dots. Excellent contrast in the veil nebula. Thank you for making such a fine filter!«

The Astronomik UHC filter stands out as the first choice for visual observation, offering enhanced contrast and detail in deep-sky objects that surpasses other filters on the market. With its Ultra High Contrast (UHC) design, the filter allows nearly 100% transmission of OIII and H-beta lines, effectively eliminating scattered light from various sources, including light pollution. This results in a significant enhancement of detail for gaseous and planetary nebulae against the sky background.Designed for versatility, the Astronomik UHC filter is effective in both urban and dark sky conditions, improving contrast for emission nebulae and other celestial objects for medium to large telescopes. It dramatically increases the visibility and detail of objects that are otherwise faint or obscured.The filter's application spans aperture ratios from 1:3 to 1:15, suitable for a wide range of telescopes. Compared to filters from other manufacturers, the Astronomik UHC filter excels in revealing more stars and finer details in celestial objects, maintaining the sharpness and optical quality expected from high-performance astronomical instruments.The filter works by blocking emission lines from high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps, the majority of emissions from LED lamps and all lines of natural airglow, while allowing H-beta and OIII lines to pass through. This selective transmission enhances the contrast between the sky background and observed objects.Additionally, the Astronomik UHC filter is recommended for observation of Jupiter's clouds and offers improved separation of double stars. In summary, the Astronomik UHC filter is indispensable for astronomers seeking to maximize visual clarity and contrast in deep-sky observation, making it an essential tool for all deep-sky observers alike.Alternatives For telescopes smaller than 5" (125mm), the Astronomik UHC-E filter with its wider pass band is more suitable.Telescopes with apertures exceeding 10" (250mm) may benefit from an Astronomik OIII visual filter as first filter.Suitability of the Astronomik UHC filtersVisual observation (dark skies): Very good, for telescopes of all aperture ratiosVisual observation (urban skies): Very good, for telescopes from 4“ (100mm) apertureTechnical dataTypical transmission of 95% at 486nm (H-beta)Typical transmission of 95% at 496nm and 501nm (OIII)Typical transmission of 95% at 656nm (H alpha)Transmission range: 480nm to 505nm and above 645nm Full-Width-Half Maximum (FWHM): 25nm Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)Finely polished optical glass, free of any striae, residual stresses, and bubblesExtremely scratch-resistant and durable coatingCompletely resistant against high humidity and aging effectsAstronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)Parfocal with other Astronomik filtersDiffraction-limitedOptimized spectral windowsDelivered in a high-quality, long-lasting filter boxDue to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.

The Astronomik UHC-E filter is tailored for deep-sky observation of emission nebulae and comets under light-polluted skies, especially ideal for smaller telescopes up to 5" (125mm) aperture. It enhances the contrast between these celestial objects and the sky background by blocking typical streetlight and LED lamp emissions, as well as all lines of natural airglow.With a Full-Width-Half Maximum (FWHM) of 45nm, the Astronomik UHC-E filter ensures a significant contrast boost while allowing a greater amount of starlight to pass through compared to its counterpart, the Astronomik UHC filter. This characteristic makes it particularly well-suited for smaller telescopes, enhancing visibility without compromising on the overall brightness. Additionally, its transmission range includes spectral lines, enhancing the observation of comets.In essence, the Astronomik UHC-E filter is a versatile tool for enhancing contrast under urban sky conditions, especially for observers using smaller telescopes to explore the depths of deep-sky objects and comets.Alternatives For telescopes larger than 5" (125mm), we recommend upgrading to the standard Astronomik UHC filter, which provides even greater contrast enhancement capabilities. For telescopes exceeding 8" (200mm), we suggest an Astronomik OIII visual filter as first filter.Suitability of the Astronomik UHC-E filtersVisual observation (dark skies): Reasonable, an Astronomik UHC filter is more suitableVisual observation (urban skies): Good, for telescopes up to 5" (125mm) apertureTechnical dataTypical transmission of 94% at 486nm (H-beta)Typical transmission of 95% at 496nm (OIII)Typical transmission of 95% at 501nm (OIII)Typical transmission of 94% at 656nm (H-alpha)Transmission range: 465nm to 530nm and above 645nm Full-Width-Half Maximum (FWHM): 45nm Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)Finely polished optical glass, free of any striae, residual stresses, and bubblesExtremely scratch-resistant and durable coatingCompletely resistant against high humidity and aging effectsAstronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)Parfocal with other Astronomik filtersDiffraction-limitedOptimized spectral windowsDelivered in a high-quality, long-lasting filter boxDue to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.