Antlia ALP-T Dualband 3.5nm SII and Hb filter

Antlia ALP-T Dualband 3.5nm SII&Hβ filter

The Antlia ALP-T Dualband 3.5nm SII&Hβ filter is specially designed to simultaneously detect emissions from Sulfur II (672.4 nm) and Hydrogen Beta (486.1 nm). It significantly improves the contrast of nebulae and delivers a higher signal-to-noise ratio (SNR), even in the presence of light pollution or moonlight. It is optimized for color cameras (OSC) but also works very well with monochrome sensors.

Key features

• Simultaneous transmission of SII (672.4nm) and H-Beta (486.1nm) lines
• Ultra-narrow bandwidth of 3.5 nm for each emission line
• OD4.5 suppression of stray wavelengths between 300 nm and 1100 nm
• Designed for color cameras, compatible with monochrome sensors
• Advanced anti-reflective coating eliminates halos and internal reflections
• Effective NIR blocking
• Recommended for use with f/4 or slower lenses (prefer Highspeed version for f/<4)

Ideal applications

• Imaging nebulae with a false-color palette (H-O-Hβ, S-H-O, H-S-OHb, etc.).
• Capture spectroscopic details invisible in conventional RGB
• Improved structure separation in SHO astrophotography
• Use under urban, suburban or rural skies (Bortle 1 to 8)

Technical specifications

• FWHM: 3.5nm +0.5/-0.5nm
• Central wavelength (CWL): SII 672.4 nm / Hβ 486.1 nm
• Maximum transmission: 90% in SII, 85% in Hβ
• Out-of-band blocking: ≥OD4.5 from 300nm to 1100nm
• Filter thickness: 2mm ± 0.05mm
• Substrate: Unglued single-piece optical glass
• Optical surface: S/D 60/40 (MIL-O-13830 standard)
• Transmitted wavefront: λ/4 or better
• Parallelism: <30 arcsec
• Mount: 2″ (M48x0.75), ultra-thin to reduce vignetting

Technology and manufacturing

• Multi-layer Ion Gun Assisted Deposition coating for maximum stability
• Eliminate halos and reduce internal reflections
• Blackened edges to eliminate stray reflections
• Durable black anodized finish and tamper-proof laser engraving
• Exceptional durability thanks to advanced Antlia coating technology

Advantages of SII&Hβ capture over SII&OIII

The decision to use an SII&Hβ band instead of SII&OIII is based on the importance of Hβ in astrophotography: although OIII is often overrepresented in RGGB matrices, Hβ reveals unique structures that are invisible with Hα, SII, and OIII alone. This enriches false-color palettes and improves the separation of subtle details in nebulae with a strong blue component.

Directions for use

• Perfect for combining with Antlia ALP-T Dualband 3nm Ha&OIII filter
• Captures all 4 spectral channels Ha, OIII, SII, Hb for ultra-rich processing
• Ideal for saving capture time with color sensors while achieving near-monochrome detail

Warnings

• Not recommended for solar imaging
• Not recommended for nighttime visual observation
• Never look directly at the sun with this filter, as serious eye damage could result.