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Baader Planetarium Baader O-III 1.25" f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 2" f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium FCCT Filter – O-III 2" unmounted (Ø 47,4 mm) f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 31mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 31mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 31mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 50x50mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 65x65mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 1.25" f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 2" f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium FCCT Filter – O-III 2" unmounted (Ø 47,4 mm) f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 31mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 31mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 31mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 50x50mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized
Baader Planetarium Baader O-III 65x65mm f/2 Highspeed-Filter (6.5nm) – CMOS-optimized

Baader Planetarium O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized

by Baader Planetarium
SKU BAA-2961225
CA$232.00 - CA$565.00
CA$232.00
CA$232.00 - CA$565.00
CA$232.00
Price Match Policy!
  • 6.5nm FWHM Bandpass for O-III
  • Optimized for f/3.4 and Faster High-Speed Optical Systems
  • Available in 1.25" & 2" Mounted, 31mm, 36mm, 47.4mm (FCCT) & 50.4mm Round Unmounted, and 50x50mm & 65x65mm Square Sizes
  • CMOS-Optimized with Reflex-Blocker™ Coatings
  • Sealed Coating Edges with Life-Coat™ Durability
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  • Description
  • FAQ
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  • Baader O-III f/2 Highspeed-Filter (6.5nm) – CMOS-optimized

    The Baader O-III f/2 Highspeed-Filter isolates the critical Oxygen-III emission line with a tight 6.5nm bandpass, engineered to maintain full transmission on optical systems as fast as f/2. Offered as mounted 1.25" and 2" filters, as unmounted round filters (31mm, 36mm, 50.4mm and a 47.4mm version for the Baader FCCT) and as 50x50mm and 65x65mm squares, it is specifically designed to counteract the bandpass shift inherent in fast optics, ensuring that your CMOS sensor captures maximum signal from planetary nebulae and supernova remnants without halos or internal reflections.

    Engineered for f/2 Systems: Maintaining Signal at Fast Focal Ratios

    Standard narrowband filters suffer from a phenomenon called bandpass shift when used with fast focal ratios; the incoming light cone is so steep that the filter's central wavelength moves, causing significant signal loss. The Baader f/2 Highspeed filter solves this by pre-shifting its bandpass, ensuring the 500.7nm O-III line remains perfectly centered when used with systems at f/3.4 and faster. This makes it an essential tool for instruments like Celestron RASA, Starizona HyperStar, and fast astrographs, where conventional filters would fail to deliver.

    6.5nm O-III for Maximum Contrast

    With a full width at half maximum (FWHM) of just 6.5nm, this filter delivers exceptional contrast by rejecting unwanted light from streetlights, moonlight, and atmospheric airglow. This narrow window dramatically darkens the sky background, making faint, extended structures in O-III rich targets like the Veil Nebula (NGC 6960) or the Dumbbell Nebula (M27) stand out with striking clarity. The high transmission within this narrow band ensures that exposure times remain manageable while detail is maximized.

    CMOS-Optimized in Every Format

    Modern CMOS sensors are highly reflective, often causing halos and internal reflections with traditional filters. Every size of this Baader Highspeed filter features advanced anti-reflection coatings, including Baader's Reflex-Blocker™ technology, to virtually eliminate these artifacts, even with bright stars in the field of view – from small sensors behind a 1.25" filter to full-frame and medium-format sensors that call for the large square formats. Additionally, Baader's Life-Coat™ technology provides a hardened, sealed coating edge, protecting the filter from moisture intrusion and aging for a lifetime of reliable use.

    Baader f/2 Highspeed vs. Standard Narrowband Filters

    The choice between a Highspeed filter and a standard narrowband filter is determined entirely by your telescope's focal ratio. A standard filter is designed for peak transmission at f/4 or slower, while this Highspeed version is specifically built for f/3.4 and faster systems.

    • Standard O-III Filter at f/2: Experiences significant bandpass shift. The filter's transmission peak moves off the O-III emission line, resulting in a dim, low-contrast image.
    • Baader f/2 Highspeed O-III Filter at f/2: The pre-shifted bandpass is perfectly aligned to the O-III line at this focal ratio, guaranteeing the highest possible signal and contrast from your fast optical system.

  • What makes the Baader 6.5nm O-III filter "Highspeed"?

    A "Highspeed" filter is specifically designed for telescopes with very fast focal ratios, such as f/2 or f/3. Its coatings are engineered to be "pre-shifted," which compensates for the blue-shift that occurs when light passes through a filter at a steep angle. This ensures the 6.5nm bandpass remains centered on the O-III emission line for maximum signal transmission on fast optics.

    Can I use this Baader f/2 Highspeed filter with a slower telescope like an f/8 refractor?

    While it will work, it is not ideal. The pre-shifted bandpass that is perfect for an f/2 system will be off-wavelength on an f/8 system, leading to reduced light transmission. For telescopes f/4 and slower, a standard Baader CMOS-optimized narrowband filter is the correct choice.

    Which size of the Baader O-III f/2 Highspeed-Filter fits my filter wheel or drawer?

    The 1.25" and 2" versions come in mounted cells for standard threaded filter holders and wheels. The 2" unmounted (Ø 47.4mm) filter is designed for the Baader FCCT (Filter Changer Camera Tilter) and will not thread into a standard 2" (M48) carousel. The 31mm, 36mm and 50.4mm unmounted round filters fit wheels that accept those sizes, such as models from ZWO, QHY or Atik, while the 50x50mm and 65x65mm squares suit filter wheels and drawers for large full-frame and medium-format sensors. Always confirm the accepted filter size in your wheel's documentation.

    Will the Baader 6.5nm O-III Highspeed filter work well for imaging the Veil Nebula (NGC 6960) with a Celestron RASA 8?

    Yes, this is a perfect combination. The Celestron RASA 8 operates at f/2, making it the exact type of instrument this filter was designed for. The Veil Nebula is extremely rich in O-III emission, and the 6.5nm bandpass will provide exceptional contrast, revealing its intricate filamentary structure against a dark sky background.

    I have a fast f/3.8 Newtonian. Is the Baader f/2 Highspeed filter a better choice than a standard O-III filter?

    No. The f/2 Highspeed filter is recommended for f/3.4 and faster, so an f/3.8 Newtonian is outside its range. Baader's standard 6.5nm O-III filter, recommended for optical systems slower than f/3.4, is the matching choice.

    What is the advantage of a 6.5nm bandpass on the Baader O-III filter compared to wider filters?

    A narrower bandpass like 6.5nm provides significantly better rejection of light pollution and natural skyglow compared to wider 10nm or 12nm filters. This leads to a darker sky background and higher contrast in your final image, making faint nebular details more visible, especially from urban or suburban locations.

  • Single or Set? Single Filter
    Filter Usage CMOS, CCD, O-III
    Type of Filter f/2 Highspeed
    Special Features CMOS-optimized with Life-Coat™
    HBW (Halfbandwidth) 6.5 nm
    CWL (Central Wavelength) 500.7 nm
    Transmission Range O-III
    AR-Coating Reflex-Blocker™ hard coated, planeoptically polished
    Suitable for f/ratio f/3.4 and faster
    Cell thread 1.25" Round Mounted: M28.5 (1.25in filter thread); 2" Round Mounted: M48x0.75 (2in filter thread)
    1.25" Round Mounted
    Net weight (kg) 0.01
    Filter size 1.25"
    Filter shape round
    Filter mounted Mounted (LPFC 6mm)
    Filter Thickness (without cell) 2 mm
    2" Round Mounted
    Net weight (kg) 0.01
    Filter size 2"
    Filter shape round
    Filter mounted Mounted (LPFC 6mm)
    Filter Thickness (without cell) 2 mm
    2" Round Unmounted Filter (Ø 47.4mm, FCCT)
    Net weight (kg) 0.01
    Filter size 47.4 mm (2" w/o cell)
    Filter shape round
    Filter mounted Unmounted
    Filter Thickness (without cell) 2 mm
    31mm Round Unmounted Filter
    Net weight (kg) 0.00
    Filter size 31 mm
    Filter shape round
    Filter mounted Unmounted
    Filter Thickness (without cell) 2 mm
    36mm Round Unmounted Filter
    Net weight (kg) 0.00
    Filter size 36 mm
    Filter shape round
    Filter mounted Unmounted
    Filter Thickness (without cell) 2 mm
    50.4mm Round Unmounted Filter
    Net weight (kg) 0.01
    Filter size 50.4 mm
    Filter shape round
    Filter mounted Unmounted
    Filter Thickness (without cell) 3 mm
    50x50mm Square Filter
    Net weight (kg) 0.02
    Filter size 50 x 50 mm
    Filter shape square
    Filter mounted Unmounted
    Filter Thickness (without cell) 3 mm
    65x65mm Square Filter
    Net weight (kg) 0.03
    Filter size 65 x 65 mm
    Filter shape square
    Filter mounted Unmounted
    Filter Thickness (without cell) 3 mm

    • Baader O-III f/2 Highspeed-Filter (6.5nm), selected size

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    • Protective Filter Case or Storage Box (packaging varies by size)

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  • Baader Planetarium Warranty Policy