Antlia designed the ALP-T Dualband 3nm Ha & OIII filter as a precision dual narrowband filter for color cameras. It transmits the red H-alpha line at 656.3nm and the blue-green OIII line at 500.7nm. This filter helps astrophotographers capture deep-sky images with a significantly improved signal-to-noise ratio (SNR). With a tight 3nm FWHM bandwidth and optical density (OD) of 4.5, it blocks unwanted light from sources like light pollution, moonlight, and airglow. As a result, it isolates Ha and OIII signals effectively and delivers enhanced contrast in nebula images.

Note: In addition to the Ha & OIII version, Antlia also offers a 3.5nm Dualband SII & H-beta filter. When used together, these two filters allow OSC camera users to record all four key narrowband emission lines—Ha, OIII, SII, and H-beta. You can separate these channels in post-processing and recombine them into custom or traditional false-color palettes, including H-O-Hb, S-H-O, H-S-OHb, and H-O-O. These combinations not only enhance visual impact but also bring out structural details that standard RGB imaging often misses.

Antlia applies advanced multi-coatings to all ALP-T dualband filters to isolate emission lines with high precision. These coatings target the H-alpha, OIII, SII, and H-beta lines while suppressing unwanted wavelengths with OD4.5 blocking. This coating performance holds up under both urban and rural skies, allowing the filters to deliver superior contrast and cleaner data in any environment.

Together, the Ha & OIII and SII & H-beta filters provide OSC users with a complete narrowband imaging solution. They improve image quality, reduce background interference, and reveal fainter details—making them ideal tools for astrophotographers seeking deeper, high-resolution views of the night sky.

Application and Performance:

• Passes OIII at 500.7nm and H-alpha at 656.3nm

• Captures the red and blue-green emission wavebands simultaneously

• Features an ultra-narrow 3nm FWHM design, allowing longer exposures and more detailed nebula capture

• Designed for colour cameras to collect cleaner data, or as a luminance filter for mono cameras to save imaging time

• Recommended for use alongside the ALP-T Dual Band SII & H-beta filter to create four-channel images (Ha, OIII, SII, H-beta) with improved signal-to-noise and better channel separation

• Suppresses unwanted wavelengths with OD4.5 optical density, increasing signal-to-noise ratio

• Blocks near-infrared (NIR) light up to 1100nm to reduce interference

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

• Works best with optics slower than f/4; for faster systems, use the pre-shifted highspeed version

• Uses Ion Gun Assisted Deposition to apply multi-layer coatings on a double-sided polished substrate for precise light pollution control

• Reduces halos and internal reflections with advanced anti-reflective halo suppression coatings

• Suppresses artificial lighting effectively from Bortle scale 1 through to Bortle scale 8

• Includes blackened edges on unmounted versions to minimise internal reflections

• Built with Antlia’s trusted coating technology for outstanding durability

• Although designed for colour cameras, the filter also performs well with monochrome cameras, helping to reduce imaging time

Spectrum Curve:

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