ZWO Narrowband SII Filter - 7nm

Narrowband filter does not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.

It 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).

Form 2018, ZWO Made a progress on narrowband filters with the new standard, provide better performance.

Technical Parameter:

Name: ZWO New narrowband 1.25″ filter

Size: 1.25″

Thickness: 5.5mm+2.5mm(thread)

Glass thickness: 1.85mm

Thread: M28.5*0.6 male thread

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.

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:

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

Reviews

https://www.cloudynights.com/topic/627187-review-of-the-new-zwo-narrowband-filters-comparison-to-the-old-zwo-and-astrodon-filters/