Antlia 3nm Pro SII filter

Antlia Sulfur II (SII) 3nm Pro filter

Interferential Filter for Astrophotography

The Antlia SII 3nm Pro filter optimizes the FWHM at 3nm. By reducing the bandwidth, this filter improves the contrast of emission targets by reducing spurious background signal. It is designed to deliver a transmission of 88% at the 672.4nm line, guaranteeing optimum signal and good nebula definition.

Wider narrowband filters often suffer significant transmission losses due to center wavelength shift (CWL). The 3nm Pro filter guarantees >88% transmission within ±1nm of the center band, enabling compatibility with lenses as fast as f/3 without significant signal loss.

Out-of-band rejection is rated OD5 (0.001%), ensuring an excellent signal-to-noise ratio and effective cutting of unwanted wavelengths. This filter is designed to limit halos around bright stars.

Application and performance

• High transmission and minimal bandwidth for optimum contrast
• Steep spectral profile to reduce halos
• One-piece substrate to eliminate internal reflections
• Target objects: SII emission nebulae, planetary nebulae, Wolf-Rayet, supernova remnants
• Can be used in polluted areas or in dark skies
• Allows photography even in the presence of the Moon
• Compatible up to f/3 with minimal signal loss
• Blackened edges to prevent reflections on unmounted models
• Superior optical reliability, less post-shooting processing
• Designed only for deep-sky objects containing SII emissions

Technical specifications

Spectral curve

Mounting ring

• 1.25'' (M28.5×0.6), 2'' (M48x0.75)
• Ultra-thin cell for reduced vignetting
• Black anodized finish, unalterable laser engraving

Available sizes

• Mounted: 1.25″, 2″
• Unmounted: Ø31mm, Ø36mm, Ø50mm, square 50x50mm

Not recommended for :

• Solar observation
• Visual observation at night

Warning:

NEVER LOOK AT THE SUN WITH THIS FILTER. Serious eye damage may occur.