The Antlia SII 4.5nm EDGE narrowband filter delivers excellent contrast and signal-to-noise ratio by tightening the FWHM (Full Width at Half Maximum) to a precise 4.5nm bandpass. Antlia integrates OD5 suppression of unwanted wavelengths and the high transmittance performance from its 3nm Pro series into this filter to ensure maximum imaging quality.

This filter reaches high transmittance at the 672.4nm SII line, letting you capture the faintest sulphur II nebula structures with clarity and precision.

Unlike broader filters that suffer significant transmission loss from centre wavelength (CWL) shifts—especially with fast systems—the SII 4.5nm EDGE maintains over 90% transmission within ±1nm of the centre band.

You can confidently use this filter across a wide range of optical setups. It performs exceptionally well with both long focal ratios and fast optics, down to f/3, with minimal loss in emission signal—fully meeting the needs of modern, high-speed systems.

Application and Performance:

• Deliver high contrast with strong transmittance and a precise 4.5nm bandwidth

• Minimise halos around bright stars with a steep spectral cutoff

• Eliminate internal reflections by using a single optical substrate

• Capture SII-rich targets, including emission nebulae, planetary nebulae, Wolf-Rayet nebulae, and supernova remnants

• Achieve clean results in both light-polluted and dark sky environments

• Keep imaging even under moonlit skies with minimal impact

• Use with fast optical systems down to f/3 while maintaining signal strength

• Block stray light effectively with edge-blackened unmounted filters

• Spend less time on post-processing thanks to stable optical performance

• Use this filter specifically for deep sky objects that emit in the SII ban

Important: This filter isn’t suitable for solar imaging or night-time visual observation.

Warning: Never look directly at the Sun using this filter. Ignoring this safety warning can result in serious and permanent eye damage.

Antlia also offers dual narrowband filters designed specifically for one-shot colour (OSC) cameras. These include the ALP-T Dualband Ha&OIII 3nm and the SII&Hb 3.5nm filters. When used together, they enable the capture of narrow-band spectral data across four channels—H-alpha, OIII, SII, and H-beta. You can separate and recombine these channels during post-processing to create a wide range of colour palettes. This flexibility allows you to boost luminance contrast in RGB-balanced images or produce false-colour combinations such as H-O-Hb, S-H-O, H-S-OHb, and H-O-O to suit your creative and scientific goals.