ZWO New narrowband 2" filter - H-Alpha 7nm

ZWO New narrowband 2″ filter

The ZWO New 2″ Narrowband Filter Set (Hα, SII, OIII) is engineered to increase contrast between emission nebulae and the night sky—without artificially brightening the target. By blocking specific wavelengths from common light-pollution sources (mercury vapor, high/low-pressure sodium lamps) and unwanted atmospheric emissions (neutral oxygen), these filters allow your deep-sky details to shine even in heavily polluted areas.

Each filter features a 7nm ±0.5nm bandpass, finely polished optical glass, and a sturdy M48×0.75 male thread mount. With a glass thickness of 1.85mm (plus 2.5mm threading), the filters deliver sharp, high-contrast images of nebulae, supernova remnants, and planetary nebulae—ideal for both visual observing and CCD/CMOS tricolor (SHO) CCD astrophotography.

Key Features

       ➠   Filter Diameter: 2″ (M48×0.75 male thread)

       ➠   Overall Thickness: 5mm + 2.5mm thread

       ➠   Glass Thickness: 1.85mm

       ➠   Bandpass (FWHM): 7 ± 0.5nm

       ➠   Transmission Rate: ~90% at each target wavelength

       ➠   Infrared Cut-Off: 700 – 1100 nm

       ➠   Optical Quality: Fine-optically polished to λ/4 wavefront accuracy on both surfaces

      ➠   Off-Band Blocking: < 0.1% (OD 3)

Individual Filter Details

• H-Alpha (Hα) Filter (7nm @ 656 nm)

  • Passes exactly 656 nm ± 3.5 nm

  • Best for revealing rich, fine nebular structures even under city lights

  • Light transmission: ~90%

• Sulfur-II (SII) Filter (7nm @ 672 nm)

  • Passes 672 nm ± 3.5 nm

  • Perfect for emission nebulae, planetary nebulae, and supernova remnants

  • Use alongside Hα and OIII for full SHO color mapping

• Oxygen-III (OIII) Filter (7nm @ 500 nm)

  • Passes 500 nm ± 3.5 nm (major OIII doublet)

  • Isolates oxygen-rich regions in nebulae

  • Enables “Hubble palette” style tricolor (SHO) imaging

Why Choose ZWO 2″ Narrowband Filters?

• High Contrast in Bright Skies: Designed to suppress common light pollution wavelengths, so your nebulae stand out sharply.

• SHO Imaging Ready: These three filters form a complete set for Hα + SII + OIII tricolor mapping—ideal for creating Hubble-style images.

• Superior Optical Quality: Each filter is polished to λ/4 wavefront accuracy, ensuring no video/CCD image degradation.

• Robust Construction: Thick glass (1.85 mm) and trusted M48×0.75 threading guarantee durability and compatibility with standard 2″ filter wheels.

Technical Data

• FWHM?7±0.5nm
• 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