ALP-T Dual Band 3nm Ha&OIII Filter 2" Mounted

The Antlia ALP-T Dual Band 3nm Ha&OIII is a 2" mounted narrowband filter designed for deep‑sky colour imaging. It passes the H‑alpha (656.3 nm) and OIII (500.7 nm) emission lines while strongly suppressing out‑of‑band light to improve contrast and signal‑to‑noise ratio on emission nebulae.

Key optical properties

The filter employs a 3 nm full‑width at half maximum (FWHM) bandpass centred on the H‑alpha and OIII wavelengths, with high peak transmission and deep out‑of‑band blocking. It also blocks near‑IR up to 1100 nm. Double‑sided multi‑layer coatings and anti‑halo treatments are used to reduce reflections and internal scattering.

Intended use

• Primarily engineered for use with colour (OSC) cameras to capture narrowband Ha and OIII signals simultaneously.
• Also applicable as a luminance/time‑saving filter when used with monochrome cameras.
• Recommended for telescopes with focal ratios slower than f/4; a high‑speed / pre‑shifted version is suggested for significantly faster optics.

Practical benefits

• Improves nebula contrast by isolating emission lines from common sources of background light such as light pollution, moonlight and airglow.
• Can be used together with Antlia’s complementary dual‑band (SII & H‑beta) filter to capture four independent narrowband channels for multi‑palette processing.

Important safety note: This filter is not suitable for solar observation. Do not look at the Sun through the filter — permanent eye damage may result.