The Antlia H-alpha 3nm Pro Highspeed 31 mm is a narrowband imaging filter designed for fast optical systems with focal ratios between f/2.6 and f/3.6. Its pre-shifted central wavelength ensures high contrast in the H-alpha emission line and an excellent signal-to-noise ratio even under light-polluted skies.

Key features

• optimized for fast f/2.6–f/3.6 optical systems through a pre-shifted central wavelength
• 3 nm FWHM bandwidth for maximum H-alpha nebular contrast
• peak transmission of about 90%
• reduced sensitivity to blue-shift effects in fast optical systems
• off-band blocking to at least OD5 (0.001%) from 300–1000 nm
• single-substrate optical construction minimizing internal reflections and halos
• high optical stability reducing the need for extensive post-processing
• suitable for imaging emission nebulae, planetary nebulae, Wolf–Rayet nebulae and supernova remnants
• effective under both light-polluted and dark skies, including bright Moon conditions
• not intended for visual observing or for solar observation
• 3-year manufacturer warranty against coating delamination

Included items

• Antlia H-alpha 3nm Pro Highspeed 31 mm unmounted narrowband filter

Technical specifications

• filter type: narrowband, hydrogen H-alpha
• diameter: 31 mm (unmounted)
• full-width at half maximum (FWHM): 3 nm
• central wavelength (CWL): 657.5 nm (pre-shifted for fast optical systems)
• peak transmission: about 90%
• off-band blocking: at least OD5 from 300 to 1000 nm
• recommended focal ratio: f/2.6–f/3.6
• applications: imaging emission nebulae, planetary nebulae, Wolf–Rayet objects and supernova remnants
• substrate: single optical-grade, non-glued
• surface quality: scratch/dig 60/40 (MIL-O-13830)
• transmitted wavefront: λ/4 or better
• surface parallelism: <30″ (arcseconds)
• filter thickness: 2.0 mm ±0.05 mm
• not recommended uses: visual observation, solar observation

Warning: NEVER look at the Sun through the Antlia H-alpha 3nm Pro Highspeed 31 mm filter. Ignoring this warning can cause permanent eye damage.