Askar 3nm duo-band filter has an extremely narrow bandwidth, and an ultra-high transmittance over 88% at its center wavelength (500.7nm and 656.3nm). Askar 3nm duo-band filter can effectively eliminate the influence of light pollution. Even if you are in an area seriously affected by light pollution, the pictures taken with the Askar 3nm duo-band filter are still very good. It is so practical and efficient that you can get astronomical images of high quality with just one duo-band filter and an ordinary astronomical colour camera.
 
The Askar 3nm duo-band filter is ideal for photographing emission nebulae, planetary nebulae or supernova remnants, and has a very high transmittance at the central wavelength. The highly narrow bandwidth of the filter effectively blocks out the effects of light pollution or other distracting factors such as night glow.
 
3nm Duo-Band Filter 2”
FWHM: 3nm
CWL: 500.7nm & 656.3nm
Peak transmittance：88%
Thickness：1.85 ± 0.05mm
Barrier property：≥OD5 @ 200-1100nm
Surface finish：60/40
Parallelism：30″