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    Narrowband Filters

    Narrowband Filters

    Hα, SII & OIII Filters | SHO Filter Sets
    $179.00 USD
    $179.00 USD $179.00 USD
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    Description
    REVIEWS
    Narrowband Filters for Astrophotography
    Narrowband filters for astrophotography isolate specific emission wavelengths while suppressing unwanted background light, helping improve contrast and signal-to-noise ratio when imaging emission nebulae.

    ToupTek Astro SHO narrowband filters are precisely tuned to the three main ionized emission lines found in star-forming regions:
    • Hα (656.3nm)
    • SII (671.6nm)
    • OIII (500.7nm)
    By using these filters, you can effectively block urban light pollution and background stray light, dramatically enhance signal contrast, and bring out incredible detail—empowering you to achieve Hubble-like color mixing (SHO synthesis) in your astrophotography.
    HSO filters for astrophotography
    Technical Parameters
    Size: 36mm (unframed) / 1.25” / 2”
    Glass Thickness: 2mm
    Transmission Range:
    • H-alpha filter: Central wavelength 656.3nm
    • SII filter: Central wavelength 671.6nm
    • OIII filter: Central wavelength 500.7nm
    Transmittance: >90%
    FWHM:
    • 36mm: H-alpha (3.5nm) / SII (4nm) / OIII (4nm)
    • 1.25” & 2”: H-alpha (6.5nm) / SII (6.5nm) / OIII (6.5nm)
    Glass Material: Quartz glass
    Frame Material: Aluminum Alloy
    Surface Treatment: Double-sided high-precision optical polishing
    Coating Technology: IAD (Ion Assisted Deposition)
    Coating System Design: AR anti-reflection coating + quartz glass + precision cutoff coating layer
    OD: ≥5.0
    HSO filters for astrophotography
    Key Features
    ▶️ Precise Band Control & Enhanced Detail Resolution
    The precise narrowband design effectively suppresses background noise while highlighting the emission structures of different elements, resulting in clearer celestial stratification and enhanced detail gradation.

    ▲ Hα filter: Central wavelength 656.3nm, FWHM 3.5nm.
    Optimized for hydrogen ionization regions, this filter serves as the primary channel for capturing nebular morphology.
    ▲ OIII filter: Central wavelength 500.7nm (OIII emission line), FWHM 4nm.
    Designed to reveal high-energy excitation zones, particularly effective for visualizing blue-green nebular details.
    ▲ SII filter: Central wavelength 671.6nm, FWHM 4nm.
    Enhances detection of faint signals and reveals structural stratification through ionized sulfur distribution. When combined with Hα, significantly improves image contrast.
    *FWHM for 1.25-inch and 2-inch filters is 6.5nm.
    ▶️ High-Quality Quartz Glass, High Transparency and Purity
    The entire series of ToupTek Astro filters utilize high-quality colorless transparent quartz glass, with >90% high transmittance, high purity, exceptional blue-violet band transmission, and outstanding thermal stability—ideal for various demanding astronomical imaging applications.
    ▶️ IAD Dense Coating, Durable and Stable
    Using IAD (Ion Assisted Deposition) coating technology, which is more costly than conventional vacuum evaporation but produces denser and more uniform coatings that are durable, corrosion-resistant, and have superior environmental stability.
    ▶️ Precision Coating, Significantly Suppresses Halos
    ToupTek Astro filters employ a proprietary multi-layer system: a single-sided cutoff coating, front surface AR anti-reflection coating, and edge blackening treatment. This combination effectively minimizes internal reflections and stray light while ensuring coating integrity and extended service life.
    ▶️ High Optical Cutoff Depth, Restores Natural Colors
    All channel filters have a cutoff depth of OD≥5.0, effectively blocking non-target spectral regions, avoiding band crosstalk and color cast, resulting in accurate and natural color reproduction.
    ▶️ Matte Black Edge Coating, Easy Installation
    The filter edge is coated with a black matte treatment to minimize stray light, which ensures transmittance, reduces glare, and enhances image contrast.
    ▲ 36mm filters: The telescope-facing side has an inward-extending blackened border for quick orientation identification.
    ▲ 1.25" & 2" filters: Feature threaded aluminum alloy frames for direct screw-in installation, ensuring fast and tool-free mounting.
    ▶️ Highly Compatible
    All filters use a single-piece, glue-free structure.
    ▲ 36mm: Recommended for APS-C and smaller cameras.
    ▲ 1.25": Recommended for cameras with a 1-inch or smaller sensor.
    ▲ 2": Recommended for full-frame and smaller cameras.
    Compatible with various brands on the market featuring 7-hole 36mm, 8-hole 1.25-inch, and 5-hole 2-inch electric filter wheels, offering a wider range of compatibility options.
    HSO filters for astrophotography
    How to Choose Narrowband Filters

    Choose your narrowband filters based on sensor size and the bandwidth available for your filter size. ToupTek Astro offers Hα, SII and OIII filters individually or as an SHO filter set.

    Sensor / Setup Recommended Size Available Narrowband Options
    1-inch or smaller sensor 1.25" Hα / SII / OIII, 6.5nm
    APS-C or smaller sensor 36mm Hα 3.5nm / SII 4nm / OIII 4nm
    Full-frame or smaller sensor 2" Hα / SII / OIII, 6.5nm or 4nm options

    4nm vs 6.5nm Narrowband Filters

    Bandwidth (FWHM) describes the width of the spectral band transmitted by the filter. A narrower bandpass isolates a tighter wavelength range, while a wider bandpass transmits a broader range around the target emission line. Choose from the bandwidth options available for your filter size and imaging setup.

    Spectrum
    3.5 and 4nm HSO filter spectrum 6.5nm HSO filter spectrum
    Spectral Chart Reading Tips:
    • The horizontal axis represents the wavelength of light (in nm), and the vertical axis represents light transmittance (percentage %).
    • Red line: Hα (656nm); Green line: OIII (500.7nm); Blue line: SII (672.4nm).
    • Emission nebula signal bands are mainly at 656nm (Hα), 500.7nm (OIII), and similar wavelengths.
    • Light pollution peaks are often found near 540nm and 590nm (sodium/mercury lamp bands).
    The transmission regions of our astronomical filters are engineered to avoid these interference bands, ensuring maximum signal clarity, enhanced contrast, and high image purity for deep-sky imaging.
    ToupTek Astro HSO Narrowband Filter Performance
    IC5070
    Photographer: voice
    Telescope: Sky-Watcher
    Mount: UMI
    Camera: ToupTek Astro ATR2600M
    Filters: ToupTek Astro 36mm LRGB&SHO
    Integration: Hα: 30 × 600s ; SII: 30 × 600s ; OIII: 30 × 600s
    Total exposure: 15h
    IC5070 Sample Image
    IC443
    Photographer: voice
    Telescope: Sky-Watcher F3.4
    Camera: ToupTek Astro ATR2600M / ATR2600C
    Mount: UMI
    Filters: ToupTek Astro 36mm HSO
    Processing: Narrowband combination using HSO channel mapping
    Total exposure: 20h
    IC443 Sample Image
    NGC2237
    Photographer: 原上行川
    Telescope: Askar SQA55
    Camera: ToupTek Astro ATR2600M
    Mount: iOptron HAE16C
    Filters: ToupTek Astro 36mm HSO
    Astrophotography wireless controller: StellaVita
    Integration: Hα: 71 ; OIII: 63 ; SII: 49
    Total exposure: 15h
    NGC2237 Sample Image
    M16
    Photographer: Yahushua
    Telescope: Askar 130HNT28-AL
    Camera: ToupTek Astro ATR585M
    Mount: iOptron CEM26
    Guide camera: G3M2210M
    Filters: ToupTek Astro 1.25” HSO
    Total exposure: 7h
    NGC2237 Sample Image
    M16 Sample Image
    NGC6357
    Photographer: voice
    Telescope: Sky-Watcher
    Camera: ASI2600M
    Filters: ToupTek Astro 2” HSO
    Mount: UMi 17
    Integration: Hα: 36 × 600s ; SII: 36 × 600s ; OIII: 36 × 600s
    Total exposure: 18h
    NGC6357 Sample Image
    Narrowband Filter FAQ

    What are narrowband filters used for in astrophotography?

    Narrowband filters isolate specific emission lines such as Hα, [OIII] and [SII] while suppressing much of the unwanted background light. They are especially useful for imaging emission nebulae and building SHO narrowband images.

    What is an SHO filter set?

    An SHO set contains SII, Hα and OIII narrowband filters. Each filter records a different emission line, and the three channels can be combined during image processing for SHO color mapping.

    Which narrowband filter size should I choose?

    Use 1.25-inch filters for cameras with a 1-inch or smaller sensor, 36mm filters for APS-C and smaller sensors, and 2-inch filters for full-frame and smaller sensors.

    Installation
    • 36mm unframed filters: Special coating eliminates ghosting. To install, align the side with the inward-extending black ring toward the telescope for instant orientation and improved convenience.
    • 1.25" & 2" filters: Special coating removes front/back orientation concerns—simply screw in for fast, tool-free installation.
    HSO filters for astrophotography
    HSO filters for astrophotography
    HSO filters for astrophotography
    Warranty and Service
    • Quality Assurance Inspection: Each filter undergoes pre-delivery spectral testing and rigorous screening to guarantee consistent optical performance.
    • After-sales Policy: Includes a two-year warranty covering manufacturing defects, plus professional technical support and usage guidance.
    • For assistance, please contact our support team:
      https://touptek-astro.com/supports
    Important Notes
    • Color Variation: Filter coating colors may appear different under varying lighting conditions and viewing angles—this is normal optical behavior.
    • Product Improvements: We continually optimize our products, which may result in minor specification and appearance updates. Specifications are subject to change without notice. Please refer to the physical product for final details.