Why does the Askar Colour Magic C1 filter have different bandwidths for H-alpha and OIII?
The asymmetrical design is a deliberate choice to improve color balance for one-shot-color (OSC) cameras. The 15nm H-alpha band provides high contrast, while the wider 35nm OIII band allows more of the typically weaker OIII signal to be captured. This helps prevent images from being overwhelmingly red and produces a more natural color result with less processing.
How does the Askar C1 filter perform in Bortle 8/9 skies?
The Askar C1 filter is highly effective in heavily light-polluted skies. Its OD3 blocking across the 200-1000nm spectrum aggressively rejects common sources of urban light pollution. By only passing the specific 656.6nm and 500.7nm wavelengths of nebulae, it dramatically darkens the sky background, allowing you to capture high-contrast images of emission nebulae even from the city.
Can I use the Askar C1 filter for imaging the Andromeda Galaxy (M31)?
No, this is not the right filter for broadband targets like galaxies or star clusters. The Askar C1 is a dual-bandpass filter that blocks almost all light except for specific emission lines. Since galaxies like M31 shine primarily in continuous-spectrum starlight, this filter would block the vast majority of their light, resulting in a very faint and incomplete image. A broadband light pollution filter is a better choice for galaxies from the city.
What kind of color balance can I expect from the Askar C1 filter on the Orion Nebula (M42)?
On a target like the Orion Nebula (M42), which is rich in both hydrogen and oxygen, the Askar C1 filter is designed to deliver a well-balanced color image with an OSC camera. The tight 15nm band will capture fine details in the red H-alpha regions, while the broad 35nm OIII band will ensure the blue-green structures in the Trapezium core are bright and prominent, avoiding an overly red final image.
Is the Askar C1 filter suitable for monochrome cameras?
While it can be used, it's not ideal. A monochrome camera cannot separate the H-alpha and OIII signals captured simultaneously by the Askar C1 filter. For monochrome imaging, it is far more effective to use separate, dedicated H-alpha and OIII single-bandpass filters to capture data for each channel individually, allowing for full processing control and palette creation (like the Hubble Palette).
What does the OD3 @ 200-1000nm rating on the Askar C1 filter mean?
OD3 stands for Optical Density 3, which means the filter blocks 99.9% of light outside its designated passbands. The @ 200-1000nm specification indicates this high level of blocking is applied across the entire spectrum from deep ultraviolet to near-infrared. This ensures a very dark, high-contrast background free from light pollution and other unwanted signals.
