The Antlia SII 3nm Pro Highspeed 36 mm is a narrowband imaging filter optimized for fast optical systems with focal ratios between f/2.6 and f/3.6. Its pre-shifted central wavelength improves SII line efficiency and delivers excellent signal-to-noise performance even under light-polluted skies.

Key features

• optimized for f/2.6–f/3.6 optical systems through a pre-shifted central wavelength
• 3 nm FWHM providing strong contrast in the sulfur SII emission line
• peak transmission of about 90%
• effective compensation of blue-shift effects in fast optical systems
• off-band blocking to at least OD5 (0.001%) between 300–1000 nm
• single-substrate construction minimizing internal reflections and halos
• blackened edges reducing stray-light reflections (unmounted filter)
• high optical stability reducing the need for extensive post-processing
• suitable for imaging emission nebulae, planetary nebulae and supernova remnants
• effective both under light-polluted and dark skies, including bright Moon conditions
• not intended for visual observing or for solar observing
• manufacturer warranty: 3 years against coating delamination

Included items

• Antlia SII 3nm Pro Highspeed 36 mm unmounted filter with blackened edges

Technical specifications

• filter type: narrowband, sulfur SII line
• diameter: 36 mm (unmounted)
• full-width at half maximum (FWHM): 3 nm
• central wavelength (CWL): 673.6 nm (pre-shifted for fast systems)
• peak transmission: about 90%
• off-band blocking: at least OD5 (300–1000 nm)
• recommended focal ratio: f/2.6–f/3.6
• applications: emission nebulae, planetary nebulae, supernova remnants
• substrate: single optical-grade, non-glued
• edge treatment: blackened edges
• surface quality: scratch/dig 60/40 (MIL-O-13830)
• transmitted wavefront: λ/4 or better
• parallelism: <30″ (arcseconds)
• thickness: 2.0 mm ±0,05 mm
• not recommended uses: visual observing, solar observing

Warning: NEVER look at the Sun through the Antlia SII 3nm Pro Highspeed 36 mm filter. Ignoring this warning can cause permanent eye damage.