The Askar C1 Duo-Band Filter: The Perfect Tool for Quality Astrophotography at an Affordable Price
Askar's ColourMagic C1 Duo-band filter is an ideal choice for astrophotographers wishing to explore the deep sky without compromising their budget. Designed to capture the Ha (Hydrogen Alpha) and OIII (Oxygen III) bands, this filter features a wide bandwidth of 35 nm for OIII and 15 nm for Ha.
This greater bandwidth, compared with narrow filters, means that the C1 filter lets through a little more of the surrounding light, which can be an advantage in moderately dark environments or for capturing more light from celestial objects. However, in heavily light-polluted urban environments, it could let through a little more spurious signal compared with narrow-band filters, designed to block light pollution sources more effectively.
That said, this relatively wide bandwidth makes the C1 filter more affordable, offering excellent value for money for amateur and semi-professional astrophotographers who want quality images without necessarily investing in more expensive narrow-band filters. What's more, the state-of-the-art transmission of over 90 % enables bright, high-contrast images to be captured, revealing the details of stars and nebulae at Ha and OIII wavelengths.
The ColourMagic C1 Duo-band filter is the perfect compromise between performance and affordability, enabling astrophotography enthusiasts to enjoy improved image quality without breaking the bank.
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)
- FWHM: OIII at 6.5 nm ± 0.5 nm, SII at 8.5 nm ± 0.5 nm
- Center wavelength (CWL): 500.7 nm and 672 nm
- Peak transmission: 85 %
- Thickness: 1.85 ± 0.05 mm
- Barrier property: ≥OD5 from 200 to 1100 nm
- Surface finish: 60/40
- Parallelism: 30″
The Super D2 Duo-narrowband filter, Askar's latest innovation, is designed for high-precision astrophotography. Featuring "Super" halo control capability, it dramatically improves the contrast of your images and eliminates unwanted halos around stars. This filter is optimized for optimum performance, even with fast telescopes up to f/1.9, delivering clear, detailed images of nebulae by capturing only specific SII and OIII band emissions.
