ZWO Duo Band Filters are dual narrowband filters primarily aimed at complementing the range of one-shot colour camerasincluding ZWO’s ASI cameras. They’re perfect for the astronomer who may already own a One Shot Colour (OSC) camera and wants to image using narrowband techniques on emission objects without purchasing a mono camera, filter wheel and narrowband filter set.

The dual band-pass nature of the Duo Band filter passes light at H (656 nm) and OIII (500 nm) wavelengths, and can greatly reduce the interference from natural light sources such as moonlight or artificial light pollution such as street lighting.

Contrast and visibility of deep sky objects such as emission nebulaeis improved.

If you’re looking for an economical solution to deep sky photography in light polluted areas ($139 for 1.25″ and $249 for 2″), the ZWO Duo Band Filters are a great choice.

The 1.85 mm Duo-Band filter can be used with most cameras and filter wheels, including ASI cameras and EFW Electronic Filter Wheels, and comes in 1.25″ and 2″ sizes.

Technical Parameters

Sizes: Standard 1.25″ & 2″

Thickness:1.85 mm

Bandwidth: HA (15 nm)OIII(35 nm)

Surface quality: 60/40 (Refer to MIL-O-13830)

Schott substrate material

More than 90% transmission atmajor OIII line486 nm, 496 nm and 501 nm

More than 80% transmission at Ha line 656.3 nm

Features

Aircraft gradealuminum with precise CNC machining

Fine sandblasting processing and anodized 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

Note on Wide Angle Applications

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.