The Antlia SII 3nm Pro narrowband filter features a finely tuned Full Width at Half Maximum (FWHM) of 3nm, providing high contrast by effectively suppressing unwanted background light and enhancing the visibility of emission structures. With a peak transmission of 88% at the 672.4nm wavelength, this filter ensures strong signal capture and sharp definition of nebulae.

Unlike broader narrowband filters, which often suffer significant transmission loss due to centre wavelength (CWL) shift, Antlia’s advanced design maintains T>88% within ±1nm of the centre bandpass. This level of precision enables reliable performance across a wide range of systems, from long focal ratio setups to fast optics as fast as f/3, with minimal signal degradation.

Out-of-band blocking is rated to OD5 (0.001%), which significantly improves signal-to-noise ratio by rejecting interference from adjacent wavelengths. Additionally, the sharp cut-off characteristics of the 3nm Pro design help reduce halo formation around bright stars, making it an excellent choice for serious astrophotographers seeking clean, high-contrast images.

Application and Performance:

• High transmittance with an ultra-narrow 3nm bandwidth maximises contrast and isolates SII emission lines

• Steep spectral profile helps minimise halos around bright stars

• Precision-crafted from a single substrate to eliminate internal reflections

• Ideal for imaging SII-rich targets such as emission nebulae, planetary nebulae, Wolf-Rayet nebulae, and supernova remnants

• Effective in both light-polluted environments and dark-sky locations

• Extends imaging opportunities during bright lunar phases by rejecting moonlight interference

• Compatible with fast optical systems down to f/3, with only minimal signal loss

• Edge-blackened filter housing reduces internal reflections caused by stray light

• Exceptional optical reliability reduces the need for extensive post-processing

• Note: This filter is only effective for deep-sky objects that emit in the SII band

NOTE – This filter is not recommended for deep sky objects that lack Oiii emission lines.