Altair 3.5nm DualBand Ha-OIII ULTRA Filter (with Individual Spectrographic Test Report)

• Beat city glow and moonlight: ultra-narrow 3.5nm FWHM windows isolate H-alpha (656.3 nm) and OIII (500.7 nm) so emission nebulae punch through severe light pollution and bright lunar phases.

• True, measured performance: each filter ships with its own 0.1 nm-resolution spectrograph report—not a batch average—so you know the exact CWL, FWHM, and transmission you’re getting.

• High transmission, low background: ~90–95% peak T on each passband with average OD6 blocking (~0.0001%) across unwanted wavelengths for maximum contrast and minimal gradients.

• Star-friendly coatings: halo-suppression AR stack plus SiO₂ hard overcoat and built-in UV/IR blocking keep stars tight and reflections under control on refractors and fast astrographs.

• Fast capture, flexible workflow: grab H-alpha + OIII simultaneously with OSC cameras to shorten integration windows; or use on mono as a high-SNR bi-color luminance source.

• Built for modern rigs: 2" (M48×0.75) cell, 1.85 mm parfocal glass (≈30 arcsec parallelism); fits Altair magnetic holders, standard 2" filter wheels, and Altair Canon/Nikon lens-to-CMOS adapters.

• Plays nicely with DSLRs & OSC: designed to pass through the Bayer matrix efficiently (works with modified and unmodified DSLRs) and pairs perfectly with sensitive OSC CMOS like Altair Hypercam.

• Scale up your palette: combine with the DualBand SII-OIII or broader TriBand/QuadBand options to expand mapping flexibility while preserving narrowband contrast.

Specifications

• Type: Dual-band ultra-narrowband line filter (H-alpha + OIII)

• Bandpasses:

  • OIII: CWL 500.7 nm, FWHM ~3.5 nm, tolerance ~±0.2 nm, T ~90–95%

  • H-alpha: CWL 656.3 nm, FWHM ~3.5 nm, tolerance ~±0.2 nm, T ~90–95%

• Blocking: Average OD6 over most out-of-band visual wavelengths

• Coatings: UV/IR-block, anti-reflection halo-suppression, SiO₂ hard overcoat

• Glass: 1.85 mm parfocal; parallelism ~30 arcsec

• Cell / Thread: 2" mounted, M48×0.75

• Camera Compatibility: OSC CMOS, mono CMOS/CCD, modified & unmodified DSLRs

• Use Cases: Severe light pollution, bright-Moon nights, short summer twilights, high-contrast bi-color imaging

What’s in the box?

• Altair 3.5nm DualBand Ha-OIII ULTRA 2" filter (M48×0.75)

• Individual spectrographic test report for this exact filter