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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