1.25 inch suits the new ZWO 8 position 1.25 inch Filterwheel

31mm unmounted suits the new ZWO 8 position 31mm Filterwheel

36mm unmounted suits the new  ZWO 7 position 36mm Filterwheel

Technical Parameter:

Name: ZWO narrowband 31mm filter

Size: D=31mm

Thickness: 2mm

The ZWO  H-Alpha filter  has a bandpass of  7nm and passes light at 656nm  wavelength, light transmission rate comes up to 80%. Best choice of narrowband H-alpha astrophotography filter for high-contrast imaging and revealing rich details of the nebula even in areas with strong light pollution.

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 nrrowband O-III 7nm filter is designed for nebula observation allowing 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!

Filter Orientation

You can judge which side faces the camera by the color like below:

New Ha filter:

New SII filter:

For New OIII filter ,Old Ha/SII/OIII filter:

1. Lay the filter down flat;
2. Put a pen on the top of it ;
3. if you can see two shadow, this side has anti-reflective coating, and it should face to the camera.4. if you can only see one shadow, this side has multilayer coating, and should face to the telescope.

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

Image Test:

Here is a test of ZWO Ha Filters (ASI1600 mono camera, single frame, 300s, DDP in MaximD)