Contrast gain for comet hunters

The Baader C2 Swan-Band filter with a bandwidth of ≤ 15 nm isolates the two carbon (C2) molecular emission lines at 511 and 514 nm. These bands, known as Swan bands after their discoverer, dominate the visible spectrum of a comet’s gas tail. The filter transmits only the light coming from these emission lines and blocks scattered background light, similar to nebula filters used in deep-sky observations. As a result, structures within the gas tail become more pronounced, even under good observing conditions.
 
The filter completely blocks the O-III line at 501 nm and below, which some other Swan-Band filters may transmit. This enables even higher contrast and makes it easier to distinguish comets with well-developed gas tails from those dominated by dust, where a Swan filter provides only a modest contrast improvement. It is an essential tool for advanced comet observers.

Advantages of Baader CMOS-optimized filters

• increased contrast, optimized for the quantum efficiency characteristics of CMOS sensors
• Reflex-Blocker™ coatings for maximum halo suppression under difficult optical conditions
• identical thickness according to industry standards, ensuring parfocality
• blackened edges all around, including a telescope-sided black rim to eliminate lateral reflections
• each filter coated individually with a sealed coating edge
• Life-Coat™ coatings ensuring exceptional durability and long-term stability, even in harsh environments

Technical specifications

• catalogue number: 2961860
• manufacturer: Baader Planetarium
• filter type: bandpass (narrowband)
• application: comet gas tails, contrast enhancement, O-III-parallel imaging
• mount: yes (LPFC 6 mm)
• size: 1.25"
• diameter: approx. 31.7 mm (1.25" standard)
• CWL (central wavelength): 513 nm (for the C2 lines at 511 and 514 nm)
• FWHM (full width at half maximum): ≤ 15 nm
• transmission range: ≤ 505–520 nm
• anti-reflection coatings: dielectric, Reflex-Blocker
• polishing: planeoptically polished
• glass thickness: 2 mm (without cell)
• weight: 10 g
• shape: round
• type: single filter
• warranty: 24 months
• EAN: 4047825054128