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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Baader 6.5nm OIII Filter - CMOS-Optimized

Baader 6.5nm OIII Filter - CMOS-Optimized

by Baader Planetarium
SKU BAA-2961175
$179.00 - $470.00
$179.00
$179.00 - $470.00
$179.00
Price Match Policy!
  • 6.5nm FWHM Bandpass
  • Optimized for Modern CMOS Sensors
  • Reflex-Blocker™ Hard Coatings
  • Available in 7 Formats (Mounted and Unmounted)
  • Plane-Parallel Substrate
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  • Description
  • FAQ
  • Specifications
  • In the Box
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  • Warranty

  • Baader 6.5nm OIII Filter - CMOS-Optimized

    The Baader 6.5nm OIII Filter isolates the critical doubly-ionized oxygen emission lines with a tight 6.5nm full-width at half-maximum (FWHM) bandpass. Available in 7 distinct formats from 1.25" round mounted to 65x65mm square, this filter is specifically engineered with Reflex-Blocker™ coatings to suppress the reflections and halos common with modern, highly-reflective CMOS sensors.

    The 6.5nm OIII Bandpass for High-Contrast Imaging

    By restricting the incoming light to a narrow 6.5nm window centered on the 500.7nm OIII line, this filter dramatically increases the contrast of emission nebulae against the skyglow background. This tight bandpass effectively eliminates light pollution, moonlight, and natural airglow, allowing faint, intricate structures within planetary nebulae and supernova remnants to become clearly visible in your images.

    Reflex-Blocker Coatings for Modern Sensors

    Modern CMOS sensors are significantly more reflective than their CCD predecessors, which can introduce halos and internal reflections around bright stars, especially in fast optical systems. Baader's CMOS-optimized design incorporates advanced Reflex-Blocker™ hard coatings, which are specifically formulated to minimize these reflections. The result is cleaner data with higher contrast, deeper blacks, and halo-free stars, allowing for more aggressive processing.

    7 Formats for Every Optical System

    To accommodate nearly any imaging setup, the Baader 6.5nm OIII filter is available in 7 different sizes. This ensures proper fitting and illumination for everything from small ZWO cameras to large-format systems with extensive filter carousels.

    • Mounted (1.25" & 2"): Standard threaded cells for universal compatibility with most filter wheels and eyepiece holders.
    • Unmounted Round (31mm, 36mm, 50.4mm): For dedicated filter wheels that require unmounted filters to maximize clear aperture and minimize weight.
    • Unmounted Square (50x50mm & 65x65mm): Designed for professional-grade cameras and large filter drawers where maximum sensor coverage is required.

  • What does "CMOS-Optimized" mean for the Baader 6.5nm OIII filter?

    "CMOS-Optimized" means the filter's anti-reflection coatings are specifically designed to handle the high reflectivity of modern CMOS sensors. This prevents halos, reflections, and other artifacts that can appear around bright stars when using filters designed for older, less-reflective CCD cameras, particularly with fast telescopes (f/5 or lower).

    How does the 6.5nm bandpass on this Baader OIII filter improve images from a light-polluted location?

    The narrow 6.5nm bandpass acts as a gate, allowing light from emission nebulae (specifically, the OIII line at 500.7nm) to pass through while blocking nearly everything else. This includes common sources of light pollution like sodium and mercury vapor streetlights, as well as natural skyglow. This dramatically darkens the sky background in your images, significantly increasing the contrast and visibility of your target.

    Is the Baader 6.5nm OIII filter suitable for visual use?

    Generally, a 6.5nm bandpass is too restrictive for satisfying visual observation, as it dims the image considerably. While it can be effective on extremely bright objects like the Orion Nebula (M42) with large-aperture telescopes (10" or more), it is primarily designed for long-exposure astrophotography where a camera can accumulate the faint signal over time.

    Which size of the Baader 6.5nm OIII filter do I need for my setup?

    The correct size depends on your camera and filter wheel. Here's a general guide:

    • 1.25" Mounted: Best for cameras with sensors smaller than the APS-C format (e.g., ZWO ASI533, ASI183).
    • 2" Mounted: Ideal for full-frame sensors or to avoid vignetting with very fast (f/2-f/4) optical systems, even with smaller sensors.
    • 31mm & 36mm Unmounted: Common sizes for specific filter wheels from brands like ZWO and QHY. Check your filter wheel's manual for the required size.
    • 50.4mm, 50x50mm, 65x65mm: For large-format sensors found in high-end astronomical cameras.

    How will the Baader 6.5nm OIII filter perform on the Veil Nebula (NGC 6960) with an 8" f/4 Newtonian?

    This filter is an excellent choice for the Veil Nebula (NGC 6960), which is a strong OIII emitter. With an 8" f/4 system, the tight 6.5nm bandpass will provide exceptional contrast, revealing the fine, filamentary details of the supernova remnant while keeping star sizes tight and free of halos, thanks to the CMOS-optimized coatings.

    Can I use the Baader 6.5nm OIII filter to image planetary nebulae like the Ring Nebula (M57) from my city backyard?

    Yes, absolutely. The Ring Nebula (M57) is a classic OIII target, and this filter is perfectly suited for imaging it from urban or suburban locations. The 6.5nm bandpass will effectively cut through light pollution, allowing you to capture the nebula's delicate structure and central star, which would otherwise be washed out by skyglow.

  • Bandpass 6.5nm
    Target Wavelength OIII (500.7nm)
    Optimization CMOS Sensors
    Available Formats 1.25" Mounted, 2" Mounted, 31mm Unmounted, 36mm Unmounted, 50.4mm Unmounted, 50x50mm Square, 65x65mm Square
    Net weight (kg) 0.01 (1.25" Round Mounted, 2" Round Mounted, 50.4mm Round Unmounted Filter)
    0.02 (50x50mm Square Filter)
    0.03 (65x65mm Square Filter)
    Filter shape round (1.25" Round Mounted, 2" Round Mounted, 31mm Round Unmounted Filter, 36mm Round Unmounted Filter, 50.4mm Round Unmounted Filter)
    square (50x50mm Square Filter, 65x65mm Square Filter)
    Single or Set? Single Filter
    Filter mounted Mounted (LPFC 6mm) (1.25" Round Mounted, 2" Round Mounted)
    Unmounted (31mm Round Unmounted Filter, 36mm Round Unmounted Filter, 50.4mm Round Unmounted Filter, 50x50mm Square Filter, 65x65mm Square Filter)
    Filter Usage CMOS, CCD, O-III
    Type of Filter Narrowband
    Special Features CMOS-optimized with Life-Coat™
    Filter Thickness (without cell) 2 mm (1.25" Round Mounted, 2" Round Mounted, 31mm Round Unmounted Filter, 36mm Round Unmounted Filter)
    3 mm (50.4mm Round Unmounted Filter, 50x50mm Square Filter, 65x65mm Square Filter)
    AR-Coating Reflex-Blocker™ hard coated, planeoptically polished
    Suitable for f/ratio > f/3.4

    • Baader 6.5nm OIII CMOS-Optimized Filter (Selected Size)

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  • Baader Planetarium Warranty Policy