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Baader C2 Swan-Band Comet Filter (15nm)
Baader C2 Swan-Band Comet Filter (15nm)

Baader C2 Swan-Band Comet Filter (15nm)

by Baader Planetarium
SKU BAA-2961860
CA$116.00 - CA$232.00
CA$116.00
CA$116.00 - CA$232.00
CA$116.00
Price Match Policy!
  • Targets C2 Swan Bands in comet gas tails
  • 15nm bandpass for high-contrast views
  • Blocks the adjacent O-III line, which is not strong in comet tails
  • Available in 1.25" and 2" mounted formats
1 in stock
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Baader C2 Swan-Band Comet Filter (15nm)

    The Baader C2 Swan-Band Comet Filter isolates faint cometary emissions within a narrow 15nm bandpass, dramatically increasing the contrast of gas tails against the skyglow. This specialized design targets the unique C2 Swan Bands, revealing delicate streamers and structures that are lost when using general-purpose nebula filters, and is available in both 1.25" and 2" mounted formats to fit any standard eyepiece or accessory.

    Isolating Comet Gas Tails: The 15nm C2 Swan-Band Advantage

    While a comet's bright dust tail is simply reflected sunlight, its ion or gas tail glows with its own distinct light. The Baader C2 Swan-Band filter is engineered with a 15nm bandpass to isolate this specific emission from diatomic carbon (C2), which is ejected from the comet's nucleus. By blocking out interfering skyglow and light from the dust tail, the filter makes the faint, ethereal structure of the gas tail visible.

    Blocking the Adjacent O-III Line

    The C2 Swan-Band filter is designated "O III parallel". Its transmission window (about 505 to 520nm, centered on 513nm) covers the two brightest C2 lines at 511 and 514nm and blocks the adjacent O-III line at 501nm, which does not predominantly occur in the tail of comets.

    C2 Swan-Band vs. UHC/O-III Filters: Why Specialization Matters for Comets

    An observer's first instinct might be to use a standard UHC or O-III nebula filter on a comet, but this is often counterproductive. Those filters are designed to block the very wavelengths the comet's gas tail emits.

    • O-III Filters: A typical O-III filter will completely block the C2 Swan Bands, effectively making the gas tail invisible while doing nothing to dim the dust tail.
    • UHC / Broadband Filters: While better than nothing, a UHC filter's bandpass is too wide, allowing significant skyglow and light from the dust tail to pass through, which reduces contrast and hides faint detail.

    The Baader C2 Swan-Band filter is the correct tool for the job. It selectively passes the light from the gas tail while rejecting the light that obscures it, delivering a view that general-purpose filters cannot match.

  • What does the Baader C2 Swan-Band filter do?

    The Baader C2 Swan-Band filter is a narrow-band filter designed to increase the contrast of a comet's gas (ion) tail. It has a 15nm bandpass that selectively transmits light from diatomic carbon (C2), which is the primary emission from the gas tail, while blocking out light pollution and excessive glare from the comet's dust tail.

    Can I use the Baader C2 Swan-Band filter for objects other than comets?

    Not really. The filter blocks the adjacent O-III line at 501nm, so it is not a substitute for an O-III or UHC filter on planetary nebulae and other emission nebulae.

    How does this 15nm C2 filter compare to a standard O-III filter for viewing nebulae?

    They do different jobs. The C2 filter's 15nm window (505 to 520nm) is centered on the Swan Bands at 511 and 514nm and blocks the O-III line at 501nm, so use a dedicated O-III filter for nebulae.

    Will the Baader C2 Swan-Band filter help me see the dust tail of a comet?

    No, the opposite is true. The dust tail shines by reflecting sunlight, which is broadband white light. This filter is designed to block most of that light to make the faint, self-luminous gas tail stand out. It will dim the dust tail and coma significantly to improve the visibility of the ion tail.

    I'm observing a bright comet with my 10" f/5 Dobsonian. Will the Baader C2 filter really make a difference?

    Absolutely. In a 10" telescope, a bright comet's coma and dust tail can be overwhelmingly bright, washing out the fainter gas tail. The Baader C2 filter will dim the coma and dust tail, darkening the background sky and allowing the delicate streamers, knots, and structure within the gas tail to become clearly visible. It often reveals a tail that was completely invisible without filtration.

    Can I use the 2" Baader C2 Swan-Band filter for imaging a planetary nebula like the Dumbbell Nebula (M27)?

    The filter can be used for imaging, but it blocks the O-III line at 501nm, so it is not suited to planetary nebulae such as the Dumbbell Nebula (M27). Use dedicated narrowband filters (O-III, H-alpha, S-II) for nebula imaging; the C2 filter is made for comet gas tails and gas plumes.

  • Bandpass 15nm
    Primary Transmission C2 Swan Bands
    O-III Line Blocks the adjacent O-III line
    Available Sizes 1.25" Mounted, 2" Mounted
    Net weight (kg) 0.01
    Filter shape round
    Single or Set? Single Filter
    Filter mounted Mounted (LPFC 6mm)
    Filter Usage Gas evolution of comets, O-III-paralel Imaging, Contrast Enhancement
    Filter Thickness (without cell) 2 mm
    CWL (Central Wavelength) 513 nm (for the C2 lines at 511 and 514nm)
    Transmission Range ≤ 505 – 520 nm
    AR-Coating dielectrically coated, planeoptically polished
    2" Mounted
    Filter size 2 inch
    Type of Filter Bandpass
    HBW (Halfbandwidth) ≤ 15nm

    • Baader C2 Swan-Band Comet Filter (Selected Size)

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  • Baader Planetarium Warranty