Antlia ALP-T Dualband 3.5nm SII&Hβ filter
The Antlia ALP-T Dualband 3.5nm SII&Hβ filter is specially designed to simultaneously capture Sulfur-II (672.4nm) and Hydrogen-Beta (486.1nm) emissions. It significantly enhances nebula contrast and delivers a superior signal-to-noise ratio (SNR), even under light pollution or moonlight. It is optimized for color cameras (OSC), but works equally well with monochrome sensors.
Key features
- Simultaneous transmission of SII (672.4nm) and H-Beta (486.1nm) lines
- Ultra-narrow bandwidth of 3.5nm for each emission line
- OD4.5 suppression of interfering wavelengths between 300nm and 1100nm
- 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 672.4nm / Hβ 486.1nm
- 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
- Mounting: 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 choice of an SII&Hβ pass instead of SII&OIII is based on the importance of Hβ in astrophotography: although OIII is often over-represented via RGGB arrays, Hβ reveals unique structures 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 night-time visual observation
- Never look directly at the sun with this filter, as serious eye damage could result.
