Colour Magic 2″ Duo-band C2 (SII+OIII)

Askar's Duo-Band C2: A Versatile and Affordable Filter for Deep Sky Images in SII and OIII

Askar's ColourMagic C2 Duo-band filter is an ideal solution for astrophotographers looking for a quality tool, specifically optimized for the SII (Sulfur II) and OIII (Oxygen III) bands. This 2-inch filter offers impressive performance, capturing the specific emissions of nebulae with a peak transmission of 90 %. Designed to capture the central wavelengths of 500.7 nm for OIII and 672 nm for SII, it guarantees clear, bright images, with enhanced contrast between celestial objects and the sky background.

The C2 filter has a wide bandwidth of 35 nm for OIII and 15 nm for SII, a choice that brings several advantages and some limitations. This relatively wide bandwidth allows more light to be captured, which is ideal for astrophotographers working in moderately dark environments and wishing to capture the details of celestial objects without the need for long exposures. However, in the presence of heavy light pollution, the C2 filter may let through slightly more ambient light than narrow-band filters, which may slightly impact image quality in urban environments.

This feature also makes the C2 filter more affordable in terms of budget, offering excellent value for money for those wishing to enjoy the benefits of SII and OIII astrophotography without investing in the often more expensive ultra-narrow band filters. What's more, the C2 filter remains perfectly suited to beginner and intermediate users, capturing detailed images of nebulae and celestial objects with rich contrast rendering.

In short, Askar's ColourMagic C2 Duo-band filter is a versatile, cost-effective choice for astrophotography enthusiasts wishing to explore the SII and OIII bands. It offers excellent image quality while remaining affordable, enabling quality shots to be taken with affordable, high-performance equipment.

1. Duo-band C1 filter (2")

• FWHM: OIII at 35 nm ± 5 nm, Ha at 15 nm ± 3 nm
• Center wavelength (CWL): 500.7 nm and 656.6 nm
• Peak transmission: 90 %
• Thickness: 2 ± 0.05 mm
• Barrier properties: OD3 from 200 to 1000 nm
• Surface finish: 60/40

This filter is ideal for astrophotography enthusiasts looking for a versatile solution for capturing both Ha and OIII emissions. With a transmission of 90 %, it guarantees clear, bright capture of nebulae.

2. Duo-band C2 filter (2")

• FWHM: OIII at 35 nm ± 5 nm, SII at 15 nm ± 3 nm
• Center wavelength (CWL): 500.7 nm and 672 nm
• Peak transmission: 90 %
• Thickness: 2 ± 0.05 mm
• Barrier properties: OD3 from 200 to 1000 nm
• Surface finish: 60/40

This filter is an excellent option for those wishing to capture SII emissions in addition to OIII. The combination of OIII and SII bands provides high-resolution images of nebulae with excellent clarity.

3. Duo-narrowband D1 (2") filter

• Width at half maximum (FWHM): OIII at 6.5 nm ± 0.5 nm, Ha at 8.5 nm ± 0.5 nm
• Center wavelength (CWL): 500.7 nm and 656.6 nm
• Peak transmission: 85 %
• Thickness: 1.85 ± 0.05 mm
• Barrier property: ≥OD5 from 200 to 1100 nm
• Surface finish: 60/40

This filter offers a narrower bandwidth, ideal for users looking to enhance the contrast of celestial objects while blocking light pollution sources. The narrow OIII and Ha bandwidths are particularly useful for urban environments where light pollution is intense.

4. Duo-narrowband D2 (2") filter (Super D)

• Width