ZWO New narrowband 1.25" filter - H-Alpha 7nm

ZWO New narrowband 1.25″ filter

ZWO's new generation of 1.25″ narrowband filters is engineered for high-contrast astrophotography, especially effective for imaging emission nebulae under light-polluted skies. These filters do not increase object brightness but significantly enhance the contrast between nebulae and the night sky.

They work by reducing the transmission of specific unwanted wavelengths, such as those from:

• Mercury vapor lamps

• High and low-pressure sodium vapor lights

• Natural skyglow caused by atmospheric neutral oxygen emissions

Since 2018, ZWO has upgraded its filter standards to deliver improved performance and consistency across all narrowband filters.

Technical Parameters

• Name: ZWO New Narrowband 1.25″ Filter

• Size: 1.25″

• Total Thickness: 5.5mm + 2.5mm (thread)

• Glass Thickness: 1.85mm

• Thread: M28.5 × 0.6 (male)

The ZWO narrowband S-II 7nm filter passes light at 672nm wavelength with a bandpass of 7nm which is designed for nebula observation. It is suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants, use it with H-alpha and OIII narrowband filters (SHO Set) for tricolor CCD astrophotography.

The ZWO narrowband O-III 7nm filter is designed for nebula observation allowing the 7nm bandwidth of light centered on a wavelength of 500nm through,  which corresponds to OIII emission lines, blocking out all other light.  Adding the ZWO O-III Narrowband filter to your imaging collection will help you go beyond the RGB imaging and will help capture your favorite nebulas in a totally new light, no matter how polluted your skies may be!

Technical Data

• FWHM?7±0.5nm
• Glass Thickness 2.0+/-0.03 mm  (1.25”/31mm/36mm)
• Fine-optically polished to ensure accurate 1/4 wavefront  over the both surfaces
• About 90% transmission at H-alpha line 656nm (H-Alpha filter )
• About 90% transmission at SII line 672nm (SII filter )
• About 90% transmission at major OIII line 500nm (OIII filter )
• Infrared wavelength 700-1100nm cut-off
• <0.1% transmission of off-band, OD3(Optical Density)

Transmission Curve

We made a test of our Ha Filters (ASI1600 mono camera, single frame, 300s, DDP in MaximDL) :