ALP-T Dual Band 5nm Ha&OIII Highspeed Filter - 2'' Mounted

The Antlia ALP-T Dual Band 5nm Highspeed filter is a dual line-pass filter intended for one-shot colour (OSC) cameras. It passes the Hα and OIII emission lines while strongly suppressing unwanted wavelengths to improve contrast on emission nebulae when imaging with fast optics.

Designed for fast optical systems

This Highspeed version shifts the passband and centre wavelength slightly to suit fast focal ratios. Antlia recommends it for optics around f/2.2 to f/3.6; the standard ALP-T 5nm is recommended for slower systems.

Performance and coatings

• Dual bandpass isolates red Hα and blue‑green OIII lines to improve signal‑to‑noise on nebulae.
• Multi‑layer coatings provide strong suppression of out‑of‑band light (manufacturer cites OD4.5 on unwanted wavelengths).
• Near‑IR blocked to the manufacturer’s specified cutoff (up to 1050 nm stated by the maker).
• Manufactured with ion‑assisted deposition on polished substrate; manufacturer reports per‑piece spectrophotometer measurement during quality control.

Use and limits

• Intended primarily for photographic use with DSLR, CMOS and CCD colour cameras; can be used in narrowband workflows to save imaging time with monochrome cameras.
• Not suitable for solar observation. Do not use for visual solar viewing.

Note: The manufacturer warns that narrowband filters can experience a blue shift at very fast focal ratios (faster than about f/2), which may reduce transmission at the emission wavelengths. This behaviour and the approximate magnitude of any shift are reported by the manufacturer; if you require exact passband curves for your optical configuration, consult the manufacturer.