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The Askar Duo-band narrowband, as its name suggests, has two passbands, which is quite different from those single-band narrowband filters thus more economical and efficient because astrophotographers don’t need to purchase a filter wheel or a whole narrowband filter set. And imagers don’t have to buy a monochrome astronomy camera as the duo-band narrowband filter goes well with ordinary color cameras. So the duo-band filter is an economical admission ticket for astrophotography lovers into the world of narrowband technology and deep-sky object imaging.
The Askar duo-band filter is suitable for imaging emitting nebulae, planetary nebulae and supernova remnants. The Askar duo-band filter has an extreme high transmission at a center wavelength of 495nm (O III) and 656.3nm (H-alpha). Narrow bandwidth enables this astroimaging filter to block all the light pollution and other unwanted artificial lights or night glow. So the Askar duo-band filter is an ideal instrument for astro-imaging in heavily light-pollution hit locations and delivers enhanced contrast at darker places.
The Askar duo-band filter is designed for improving the contrast and details of nebulae and supernova remnants. Featuring extreme narrow bandwidth and a greatly high transmission at a center wavelength of 495nm and 656.3nm, the Askar duo-band filter can bring out the most amount of details of the emission nebulae, planetary nebulae and supernova remnants. Also, the out-of-band blocking ability is rated with OD3 (0.1%) with the blocking range of 200-1100nm. It delivers an excellent signal-to-noise ratio and a sharp cut-off rate to attenuate the disturbance from other wavelengths.
The narrow bandwidth and an effective cut-off rate are important indices when choosing a narrowband filter. The Askar duo-band filter has a narrow bandwidth and an extreme transmission of more than 95% at 495nm and 656.3nm, in the meanwhile, sufficiently suppressing other off-band wavelength. So the Askar O III filter can efficiently reject all the light pollution. You can expect a terrific performance of this duo-band filter in artificially-brighten background sky with your astronomy cameras (like the ZWO’s ASI series color cameras).
The production process is strictly controlled and every single Askar duo-band narrowband filter is individually examined and tested to ensure that they can highly satisfy the observing interests and needs of our customers.


· Narrow bandwidth, properly designed for astrophotography both in light polluted or dark locations.
· Useful for imaging emission nebulae, planetary nebulae and supernova remnants.
· High transmission and sharp cut-off can greatly enhance the contrast and bring out the most detailed information for those deep-sky objects.
· Designed to sharply cut off the inference of artificial light from sodium vapor or mercury vapor street lights and other unwanted disturbance like sky glow.
· The Askar duo-band narrowband filter is not suitable for visual observation and not designed for imaging or observing the Sun.