ZWO 1.25'' Duo-Band Dual Narrowband Filter

ZWO 1.25" Duo-Band Dual Narrowband Filter

  (2 Reviews)
✓ 2 year warranty


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About this product

Model:  zwo_duo-band_125
Part Number:  ZWO-DB1.25

New ZWO Dual Narrowband Filter - Image using narrowband techniques through a colour camera

ZWO Duo-Band Filter is a dual narrowband filter primarily aimed at complementing the ZWO range of colour ASI cameras. The Duo-Band filter is aimed at the astronomer who may already own a One Shot Colour (OSC) camera and wants to image using narrowband techniques or emission objects without purchasing a mono camera, filter wheel and narrowband filter set.

The Duo-Band filter offers an economical entry into the world of narrowband imaging and can also offer a practical solution to imaging in light polluted urban areas.

The dual band pass nature of the Duo-Band filter passes light at Hα (656nm) and OIII (500nm) wavelength, and can reduce the interference from natural light sources such as moonlight, or artificial light pollution such as street lighting. It can help improve the contrast and visibility of deep sky objects such as emission nebula using a OSC camera. If you are looking for a solution to deep sky photography in light pollution area, then ZWO Duo-Band Filter will be a great choice.

The Duo-Band filter can be used with all ASI cameras and EFW Electronic Filter Wheel and comes in 1.25” and 2” sizes.


  • Aerometal material. Precise CNC machining
  • Fine sandblasting process and anodised finish
  • Extinction treatment to prevent reflection
  • Laser engraving font that will never fade
  • Precise double-sided optical coating
  • Fine-optically polished to ensure accurate 1/4 wavefront and <30 seconds parallelism over the both surfaces

 Transmission Chart

Usage Tips

The incoming light transmitted through the filter should be perpendicular to the filter, or the incident angle should be less than 8°. Therefore, this product is not suitable for wide-angle or ultra wide-angle lenses.

Test Results

Images captured with ASI colour cameras and Duo-Band Filters. You can see that the potential for deep space photography in strong light polluted areas is vastly improved with the Duo-Band filters.


  • Name: ZWO Duo-Band Filter
  • Size: Standard 1.25” & 2”
  • Thickness: 1.85 mm
  • Bandwidth: HA (15nm) OIII (35nm)
  • Surface quality: 60/40 (Refer to MIL-O-13830)
  • Schott substrate material
  • More than 90% transmission at major OIII line 486.nm1, 496nm and 501nm.
  • More than 80% transmission at Ha line 656.3nm

Customer reviews

Average Rating (2 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Doesnít fit a Dwarf 2 filter holder
26 October 2023  | 

Bought this for my Dwarf 2 smart scope as it takes 1.25Ē filters and the ZWO duo band is the recommended filter for the Dwarf 2. However the filter doesnít fit the filter holder. It wonít screw tight and it is loose and falls out. Iím not sure if this a ZWO issue with their thread (it has very little threaded part compared to the ND and UHC filter that came with the scope). Rather than send back I have used some plumbers tape on the thread to increase the size and it now screws tight. Shouldnít have to do this for an £86 filter but this is no fault of FLO who as usual provided fast dispatch.

Canít yet comment on the filter itself in terms of Astrophotography but online reviews suggest it should do the job intended. I will also look at the Optolong L-enhance as itís another suggested filter that doesnít break the bank.

Rating (max 5):  
Zwo duo band filter
01 July 2023  | 

Arrived on time excellent service as usual. I have used the filter once and it performed as expected. Good quality item


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