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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 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II
Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II

Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II

by Baader Planetarium
SKU BAA-2961680
$946.00 - $2,105.00
$946.00
$946.00 - $2,105.00
$946.00
Price Match Policy!
  • 3.5nm (H-alpha, S-II) and 4nm (O-III) Bandpasses
  • Optimized for f/2 Ultra-Highspeed Optical Systems
  • CMOS-Optimized with Reflex-Blocker™ Coatings
  • Pre-Shifted Center Wavelengths to Counteract Band-Shift
  • Life-Coat™ Hard Coatings for Extreme Durability
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  • Description
  • FAQ
  • Specifications
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  • Warranty

  • Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set - CMOS-Optimized H-alpha/O-III/S-II

    The Baader 3.5/4nm f/2 Ultra-Highspeed Filter Set is engineered specifically for modern, fast astrographs like Celestron RASA and HyperStar systems. This CMOS-optimized trio features ultra-narrow 3.5nm H-alpha and S-II filters and a 4nm O-III filter, all pre-shifted to place their transmission peaks precisely on the emission line when used in an f/2 light cone. This design corrects for the inherent blue-shift that occurs with fast optics, ensuring you capture maximum signal without the transmission loss typical of standard narrowband filters on systems faster than f/3.

    Engineered for f/2 Systems: Pre-Shifted for Maximum Signal

    Standard narrowband filters suffer from band-shift when used in optical systems faster than f/4; the steep light cone shifts the filter's transmission curve toward blue, causing it to miss the target emission line. Baader's f/2 Ultra-Highspeed filters solve this by intentionally shifting the center wavelength during manufacturing. This ensures that at f/2, the filter's passband is perfectly centered on the 656.3nm, 500.7nm, or 672.4nm lines, delivering nearly 100% of the available signal to your sensor.

    CMOS-Optimized Coatings: Halos and Reflections Suppressed

    Modern CMOS sensors are notoriously reflective, often creating halos and internal reflections when paired with traditional filters. Every filter in this f/2 set features Baader's Reflex-Blocker™ hard coatings and plane-optically polished surfaces. These treatments drastically reduce reflections, eliminating the halos around bright stars that can ruin an otherwise perfect image. Additionally, Baader's Life-Coat™ technology provides a hardened, scratch-resistant surface that withstands harsh cleaning and environmental conditions for years of use.

    3.5nm & 4nm Bandpasses: Extreme Contrast for Emission Nebulae

    With a full width at half maximum (FWHM) of just 3.5nm for H-alpha and S-II, and 4nm for O-III, these filters provide an extreme signal-to-noise ratio. This ultra-narrow bandpass rejects moonlight, city light pollution, and natural skyglow more effectively than wider 6.5nm or 7nm filters. The result is a darker background and significantly higher contrast, allowing faint structures within objects like the Pelican Nebula (IC 5070) or the Heart Nebula (IC 1805) to be recorded with greater clarity.

    Baader f/2 Ultra-Highspeed vs. Standard f/4+ Narrowband Filters

    While standard narrowband filters offer excellent results on slower systems, their performance degrades sharply at f/2. This set is purpose-built for that specific application.

    • Standard 7nm Narrowband Filters: These are more forgiving on a wider range of focal ratios from f/4 to f/10. However, placed in an f/2 system, their passband shifts so far that they may only transmit 50% or less of the target emission line's light.
    • Baader f/2 Ultra-Highspeed Filters: These are optimized for peak transmission from f/1.8 to f/3.5. On a slower f/8 system, their pre-shifted bandpass would be off-target in the other direction, reducing their effectiveness. They are a specialist tool for a specialist optical system.

  • Can I use the Baader f/2 Ultra-Highspeed filters on my f/8 SCT?

    It is not recommended. These Baader f/2 filters are "pre-shifted," meaning their center wavelength is intentionally offset to land perfectly on the emission line in a very fast f/2 light cone. On an f/8 system, this pre-shift would place the transmission band off-target, resulting in significant signal loss. For f/4 or slower systems, Baader's standard 6.5nm or 7nm narrowband filters are the correct choice.

    What does "CMOS-optimized" mean for the Baader 3.5/4nm filter set?

    CMOS-optimized refers to several design features that combat issues common with modern CMOS sensors. These include Reflex-Blocker™ coatings to prevent halos from reflections between the sensor and filter, plane-optically polished surfaces for sharpness, and sealed coating edges to prevent moisture intrusion. This ensures clean, artifact-free images even with bright stars in the field of view.

    How will the 3.5nm bandpass on the Baader f/2 filters affect imaging the Veil Nebula (NGC 6960) from my city backyard?

    The ultra-narrow 3.5nm bandpass is extremely effective at isolating the specific light from the Veil Nebula while rejecting broad-spectrum light pollution from city skies. This drastically increases contrast, making the faint, filamentary structure of the nebula stand out against a dark background. Even with an f/2 system's fast light-gathering ability, this level of filtering is critical for pulling out detail from light-polluted locations.

    Why are the H-alpha and S-II filters 3.5nm while the Baader O-III filter is 4nm?

    This is a deliberate engineering choice. The O-III emission line is generally fainter in most nebulae compared to H-alpha. The slightly wider 4nm bandpass for O-III allows for slightly more signal to be gathered, improving the signal-to-noise ratio for this critical wavelength without compromising too much on contrast. The H-alpha and S-II lines can be filtered more aggressively at 3.5nm for maximum background rejection.

    Are these Baader 3.5/4nm filters parfocal?

    Yes, all Baader filters within a given size and series are designed to be parfocal. This means you should not need to make significant, if any, focus adjustments when switching between the H-alpha, O-III, and S-II filters in this set, saving valuable imaging time.

    Will the Baader f/2 Ultra-Highspeed filter set work with my Celestron RASA 8 at f/2?

    Absolutely. This filter set is designed precisely for instruments like the RASA 8. The f/2 optimization ensures you get maximum signal transmission by counteracting the band-shift inherent to the RASA's f/2 optical design, making this set a perfect match for unlocking the full potential of your astrograph.

  • Filter Set H-alpha, O-III, S-II
    H-alpha Bandpass 3.5nm FWHM
    O-III Bandpass 4nm FWHM
    S-II Bandpass 3.5nm FWHM
    Primary Optimization f/1.8 to f/3.5 optical systems
    Coatings Reflex-Blocker™ and Life-Coat™ Hard Coatings
    Substrate Plane-optically polished
    Available Sizes 1.25" Mounted, 2" Mounted, 31mm Unmounted, 36mm Unmounted, 50.4mm Unmounted, 50x50mm Unmounted, 65x65mm Unmounted
    Net weight (kg) 0.02 (1.25" Round Mounted)
    0.04 (2" Round Mounted, 50.4mm Round Unmounted Filter)
    0.01 (31mm Round Unmounted Filter, 36mm Round Unmounted Filter)
    0.06 (50x50mm Square Filter)
    0.10 (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)
    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, H-alpha, O-III, S-II
    Type of Filter f/2 Ultra-Highspeed
    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)
    CWL (Central Wavelength) 656.3 nm / 500.7 nm / 671.7 nm
    AR-Coating Reflex-Blocker™ hard coated, planeoptically polished
    Suitable for f/ratio < f/2.3

    • H-alpha 3.5nm f/2 Ultra-Highspeed Filter

      × 1

    • O-III 4nm f/2 Ultra-Highspeed Filter

      × 1

    • S-II 3.5nm f/2 Ultra-Highspeed Filter

      × 1

    • Individual Filter Cases

      × 3

  • Baader Planetarium Warranty