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 (One Shot Colour) 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.

Precision CNC machined from Aircraft grade alloys,hard anodised finished Cell with Laser engravings, finely polished optical surface to ensure 1/4 wavefront and <30 arc seconds parallelism over the both surfaces. Precise double sided coatings with anti-reflection coatings.

ZWO Duo-Band Filter Technical Specification:

• Size: Standard 1.25”
• 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

Note:  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 color 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.