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July 1st: Store will be closed for Canada Day. Orders placed that day will ship on July 2nd.
ZWO Duo-Band Filter

ZWO Duo-Band Filter

by ZWO
SKU ZWO-DB1.25
$79.00 - $149.00
$79.00
$79.00 - $149.00
$79.00
Price Match Policy!
  • Passes H-Alpha (15nm) and OIII (35nm) Wavelengths
  • Designed for One-Shot Color (OSC) Cameras
  • 1.25" Threaded Cell
  • Over 80% Ha & 90% OIII Transmission
  • 1/4 Wavefront Polished Substrate
7 in stock
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • ZWO 1.25" Duo-Band Filter

    The ZWO 1.25" Duo-Band Filter makes narrowband imaging possible for color cameras by isolating the two most critical emission nebula wavelengths. It captures H-Alpha (656.3 nm) in a 15 nm bandpass and OIII (500 nm) in a 35 nm bandpass, with transmission rates exceeding 80% and 90% respectively. This dual-band approach dramatically increases contrast on emission targets, allowing you to capture clean, detailed data from light-polluted locations with your existing one-shot color camera.

    Capture Narrowband Data with Your OSC Camera at Over 90% Transmission

    This filter is the most direct path to narrowband imaging for any astronomer with a color CMOS or CCD camera. By simultaneously passing both the deep red of Hydrogen-alpha and the teal-blue of Oxygen-III, it collects the primary structural and detail wavelengths of emission nebulae in a single exposure. This eliminates the need for a monochrome camera, filter wheel, and separate SHO filter set, significantly simplifying your imaging train and reducing total acquisition time.

    15nm Ha & 35nm OIII Bandpasses Optimized for Signal

    The ZWO Duo-Band filter features a 15 nm bandpass for H-Alpha and a wider 35 nm bandpass for OIII. This design is a deliberate trade-off, balancing interference rejection with the signal requirements of a color sensor's Bayer matrix. These wider-than-typical bandpasses allow more photons to reach the sensor, which is critical for achieving a strong signal-to-noise ratio with an OSC camera in reasonable exposure times, while still blocking the vast majority of light pollution from city lights and moonlight.

    ZWO Duo-Band Filter vs. A Full Monochrome Setup

    A dedicated monochrome camera with a filter wheel and 3nm or 5nm narrowband filters will always provide the highest possible resolution and data separation. That setup allows for precise control over each channel for complex Hubble Palette (SHO) processing. However, the ZWO Duo-Band Filter with a color camera grants access to high-contrast nebula imaging at a fraction of the cost, complexity, and setup time. For imagers in light-polluted skies who want to capture stunning nebulae without investing in a second complete imaging system, the Duo-Band filter is the more pragmatic solution.

    1/4 Wavefront Optics & Anti-Reflection Build

    Each Duo-Band filter is built on a Schott substrate, polished to a 1/4 wavefront accuracy to ensure your telescope's resolution is not compromised. The 60/40 surface quality meets MIL-O-13830 standards, and the filter cell itself is CNC machined from aircraft-grade aluminum. An anodized finish and internal extinction treatments prevent reflections and internal glare from degrading your final image, preserving the high contrast this filter is designed to create.

  • How will the ZWO Duo-Band Filter perform on the Orion Nebula (M42) with a color camera?

    The ZWO Duo-Band filter is excellent for the Orion Nebula (M42). It will isolate the rich Hydrogen-alpha signal in the outer wings and the strong Oxygen-III emission in the Trapezium core. From a light-polluted site, this filter will dramatically darken the sky background, making the nebula's structure and color far more prominent than with a standard light pollution filter.

    Can I image galaxies like Andromeda (M31) with the ZWO Duo-Band Filter?

    No, this filter is not recommended for broadband targets like galaxies or star clusters. Galaxies emit light across the entire visible spectrum. The Duo-Band filter blocks almost all of that light, passing only the H-alpha and OIII wavelengths. While you would capture the small emission nebulae within M31's arms, the galaxy's core and dust lanes would be almost completely filtered out. Use a broadband light pollution filter for galaxies.

    Why are the H-Alpha (15nm) and OIII (35nm) bandpasses different widths on the ZWO Duo-Band Filter?

    The different bandpass widths are an intentional design choice for use with one-shot color cameras. The wider 35 nm OIII bandpass allows more signal to pass through the Bayer matrix of the sensor, which is less sensitive to these wavelengths. The tighter 15 nm Ha bandpass provides higher contrast on the stronger hydrogen signal, balancing signal strength with rejection of nearby light pollution sources.

    Is the ZWO Duo-Band Filter a good replacement for a monochrome camera setup?

    It is an excellent alternative, but not a direct replacement. A monochrome camera with separate, very narrowband (e.g., 3nm) filters offers superior data isolation for advanced processing techniques like the Hubble Palette. The ZWO Duo-Band Filter provides a much simpler and more affordable way for OSC camera users to achieve the high-contrast results of narrowband imaging on emission nebulae, without the cost and complexity of a full mono system.

    Will the 1.25" ZWO Duo-Band filter work in my ZWO EFW filter wheel?

    Yes, the ZWO 1.25" Duo-Band Filter is threaded to mount directly into any ZWO electronic filter wheel (EFW) that accepts 1.25" filters. It can also be threaded directly onto any 1.25" nosepiece or accessory with standard filter threads.

    What does the 60/40 surface quality specification mean for the ZWO Duo-Band Filter?

    This specification refers to the optical polish and surface imperfections based on the MIL-O-13830 military standard. The "60" refers to the maximum allowable scratch width in microns, and the "40" refers to the maximum allowable dig or pit diameter in hundredths of a millimeter. A 60/40 rating indicates a high-quality optical surface suitable for demanding imaging applications, ensuring minimal light scatter and preserved image contrast.

  • SKU ZWO-DB1.25
    Filter Type Dual Narrowband Pass (Ha, OIII)
    Size 1.25" (31.75mm)
    Mounting Threaded Cell
    H-Alpha Bandpass 15 nm
    OIII Bandpass 35 nm
    H-Alpha Transmission >80% at 656.3 nm
    OIII Transmission >90% at 486nm, 496nm, and 501nm
    Wavefront Accuracy 1/4 Wavefront
    Substrate Schott Glass
    Thickness 1.85 mm
    Surface Quality 60/40 (per MIL-O-13830)
    Shape Round

    • ZWO 1.25" Duo-Band Filter

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  • ZWO 2-Year Limited Warranty