ZWO New narrowband 1.25" filter - 7nm set

ZWO New narrowband 1.25″ filter

ZWO New 1.25″ Narrowband Filters – Reveal Nebulae in Stunning Detail

The ZWO New 1.25″ Narrowband Filter Set (Hα, SII, OIII) brings sharp, high-contrast imaging to astrophotographers working under light-polluted skies. These filters do not brighten objects but instead suppress artificial light and atmospheric skyglow, enhancing contrast between nebulae and background sky.

With a 7nm ±0.5nm bandpass, each filter blocks unwanted wavelengths from mercury and sodium vapor lamps and atmospheric emissions, allowing precise transmission of light from emission nebulae.

From 2018 onwards, ZWO improved the design standard for better performance and more consistent results in both visual and imaging applications.

Key Features

     ➤   Filter Size: 1.25″ (M28.5×0.6 male thread)

     ➤   Total Thickness: 5.5mm + 2.5mm thread

     ➤   Glass Thickness: 1.85mm

     ➤   Bandpass (FWHM): 7 ± 0.5nm

     ➤   Transmission Rate: ~90% at key wavelengths

     ➤   Infrared Cut-Off: 700 – 1100 nm

     ➤   Optical Quality: λ/4 wavefront accuracy, fine-polished

     ➤   Blocking Power: <0.1% off-band transmission (OD3)

Filter Specifics

     ➤   H-Alpha (Hα) 7nm @ 656 nm

          ➠   ~90% transmission at 656 nm

          ➠   Excellent for enhancing red nebulae details

          ➠   Best suited for narrowband deep-sky imaging under heavy light pollution

     ➤   Sulfur-II (SII) 7nm @ 672 nm

          ➠   Ideal for capturing emission and planetary nebulae

          ➠   Works in tricolor setups with Hα and OIII (SHO)

          ➠   High contrast for rich structural details

     ➤   Oxygen-III (OIII) 7nm @ 500 nm

          ➠   Targets OIII emission lines precisely

          ➠   Suitable for planetary nebulae and supernova remnants

          ➠   Blocks unwanted light and isolates oxygen-rich regions

What Sets ZWO 1.25″ Filters Apart?

     ➤   Improved Standard Since 2018 – Enhanced optical performance and tighter tolerances.

     ➤   SHO Imaging Ready – Combine Hα, SII, and OIII filters for Hubble-style tricolor imaging.

     ➤   Excellent Build & Polish – Glass polished to λ/4 accuracy ensures excellent image quality.

     ➤   Works with Monochrome Cameras – Perfect match for cameras like ASI1600MM Pro.

     ➤   Infrared Blocking – Cuts IR up to 1100nm to ensure crisp images with no sensor bleed.

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) :