ZWO New narrowband 2" filter - Olll 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