Altair DualBand ULTRA 3.5nm Filter 2" COMBO (Ha+OIII + SII+OIII)

This combo is basically the cheat code for SHO-style nebula imaging with a color (OSC) camera. You get two separate 3.5nm DualBand filters—one for Ha+OIII and one for SII+OIII—so you can split Ha and SII into separate channels while also collecting twice the OIII data (because OIII is present in both filters). The result: cleaner channel separation, more usable signal per night, and serious performance in bright moonlight or extreme city light pollution.

• Bundle includes both DualBand ULTRA filters for a lower price than buying separately
• Designed for One Shot Colour (OSC) CMOS cameras (also useful with mono for luminance-style data)
• Enables proper SHO/Hubble palette workflows with a color camera
  • Ha and SII are separated into different filters
  • OIII is captured in both filters, giving 2x the OIII data when used together
• Built for bright moonlight and extreme light pollution (major city center conditions)
• Ultra-narrow 3.5nm FWHM with steep bandpasses for maximum contrast and signal vs background
• OD6 blocking (≈0.0001%) across most unwanted wavelengths for strong suppression of skyglow and artificial lighting
• Halo suppression anti-reflective coatings for cleaner stars
• UV/IR blocking included (works with modified and unmodified DSLRs too)
• Strong performance with fast optics
  • Best performance at focal ratios as fast as f/4.8, with contrast improving as focal ratio slows
• Standard 2" M48x0.75 thread
  • Fits standard 2" filter wheels and holders (including Altair magnetic holders and common DSLR lens-to-camera adapters)
• Individually tested and certified
  • Each filter includes its own professional spectrographic test report (0.1nm resolution), not a generic batch report

Specifications

• Format: 2" mounted, M48x0.75 thread
• Set contents:
  • DualBand Ha + OIII ULTRA (3.5nm)
  • DualBand SII + OIII ULTRA (3.5nm)
• Bandpass width: 3.5nm FWHM (steep bandpasses for high contrast)
• Blocking: OD6 (≈0.0001%) over the majority of unwanted wavelengths
• Glass thickness / parfocality: 1.85mm optical glass, parfocal
• Parallelism: 30 arc sec
• Coatings: SiO2 hard overcoat + UV/IR block + anti-reflection / halo suppression
• Recommended optics speed: Best down to f/4.8 (contrast increases as focal ratio increases)

DualBand SII + OIII ULTRA (3.5nm)

• OIII: CWL 500.7nm, FWHM tolerance ~0.2nm, Transmission 90–95%
• SII: CWL 671.6nm, FWHM tolerance ~0.2nm, Transmission 90–95%

DualBand Ha + OIII ULTRA (3.5nm)

• OIII: CWL 500.7nm, FWHM tolerance ~0.2nm, Transmission 90–95%
• Ha: CWL 656.3nm, FWHM tolerance ~0.2nm, Transmission 90–95%

What’s in the box?

• 3.5nm DualBand Ha + OIII ULTRA 2" filter
• Individual spectrographic test report for the Ha+OIII filter
• 3.5nm DualBand SII + OIII ULTRA 2" filter
• Individual spectrographic test report for the SII+OIII filter

Software and Docs

• Individual spectrographic test reports (included for each filter)