ZWO SII 7NM FILTER 1.25"

Narrowband filters do not eliminate the effects of light pollution or increase the object’s brightness, but rather increase the contrast between nebula and night sky. 

They can reduce the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).

Technical Parameters:

Name: ZWO New narrowband 1.25″ filter

Size: 1.25″

Thickness: 5.5mm+3.5mm (thread)

Thread: M28.5*0.6 male thread

The ZWO narrowband S-II 7nm filter passes light at a 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 for tricolor CCD astrophotography.

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 SII line 672nm (SII filter )
• Infrared wavelength 700-1100nm cut-off
• <0.1% transmission of off-band, OD3(Optical Density)

Transmission Curve

New Narrowband & Old Narrowband filter:

The new SII filter is based on the new base glass, less reflection (less halo of bright stars).