The Antlia ALP-T Dual Band 5nm SII & H-beta filter is a precision-built dual line-pass filter. It transmits deep red Sulfur-II (SII) and blue Hydrogen-beta (H-beta) emission lines. Antlia designed it for one-shot color (OSC) cameras such as DSLRs and dedicated astronomy cameras. As a result, this filter expands OSC imaging by allowing users to capture narrowband signals beyond the more commonly used Ha and OIII lines.

Moreover, it works seamlessly alongside the ALP-T Ha & OIII filter. When used together, these filters let you capture all four major emission lines—Ha, OIII, SII, and H-beta. You can then separate and recombine each spectral channel in post-processing. This process enables the creation of a wide variety of false-color palettes, including H-O-Hb, S-H-O, H-S-OHb, and H-O-O. These combinations enhance visual impact and help bring out faint structural details within emission nebulae. In particular, the SII & H-beta filter significantly boosts contrast, allowing nebulae to stand out more clearly against the background.

Instead of pairing SII with OIII, Antlia chose to combine SII with H-beta for a deliberate reason. H-beta, although often overlooked, is the second strongest hydrogen emission line after H-alpha. It lies in the blue region of the spectrum and reveals features that H-alpha, OIII, or SII alone may not capture. Meanwhile, OIII is already well represented in OSC imaging thanks to the RGGB Bayer pattern, which includes twice as many green pixels. Because of this, OSC sensors naturally capture OIII with high efficiency. In fact, users can still extract a strong OIII signal by isolating the green and blue channels using the Ha & OIII filter and then synthesizing a dedicated OIII channel.

That said, if your goal is to simply enhance Ha & OIII data with SII, a dedicated SII filter might provide a cleaner signal. However, the SII & H-beta filter offers added value. It captures the rare H-beta signal, boosts image contrast, and reveals subtle features that enrich your final result.

Importantly, both the Ha & OIII and SII & H-beta filters in the ALP-T 5nm series share the same advanced multi-coatings. These coatings isolate key emission lines with remarkable precision while suppressing unwanted light. Thanks to an optical density rating of OD4.5, both filters cut through light pollution, moonlight, and airglow. As a result, they deliver cleaner signals, stronger contrast, and higher image quality even under challenging conditions.

In summary, when used together, the ALP-T Ha & OIII and SII & H-beta filters unlock the full potential of narrowband imaging for OSC users. You’ll capture cleaner data, generate richer color palettes, and produce detailed, high-contrast images of the night sky.

Application and Performance:

• Transmits the SII emission line at 672.4nm and the H-beta line at 486.1nm

• Optimized for use with DSLR, CMOS, and CCD color cameras

• Features an ultra-narrow 5nm FWHM, allowing for longer exposure times and better contrast

• Pairs effectively with the ALP-T Dual Band 5nm Ha & OIII filter to capture four distinct channels (Ha, OIII, SII, H-beta) with improved signal-to-noise and clearer separation

• Blocks unwanted wavelengths with OD4.5 optical density, enhancing overall image clarity

• Includes steep bandpass curves and blackened edges (for unmounted versions) to minimize internal reflections

• Maintains spectral accuracy with a flat-top, moderate bandpass that limits spectrum shift

• Uses Ion Gun Assisted Deposition on a double-sided polished substrate for consistent, high-precision light pollution suppression

• Effectively reduces artificial lighting from Bortle 1 to Bortle 8 environments

• Also compatible with monochrome cameras for faster narrowband data collection

• Blocks near-infrared (NIR) wavelengths up to 1100nm to prevent image contamination

Spectrum Curve:

Samples:

Filter Ring:

2” (M48*0.75)

Ultra-thin filter cell to minimize vignetting by maximize possible clear aperture

Black Anodized Finish

Laser Engraving No Fading

Not Recommended:

Solar imaging

Night visual observation