The Antlia H-alpha 3nm Pro Highspeed 2" 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 ensures very strong H-alpha contrast and an excellent signal-to-noise ratio even under light pollution or bright Moon conditions.

Key features

• optimized for f/2.6–f/3.6 systems thanks to the pre-shifted central wavelength
• 3 nm FWHM for maximum H-alpha nebular contrast
• peak transmission of about 90%
• compensation of blue-shift effects typical of 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
• ultra-thin 2" filter cell minimizing vignetting and maximizing clear aperture
• black anodized housing with laser-engraved markings
• suitable for emission nebulae, planetary nebulae, Wolf–Rayet nebulae and supernova remnants
• effective under both light-polluted and dark skies, even with the Moon above the horizon
• not intended for visual observing or for solar observing
• 3-year manufacturer warranty against coating delamination

Included items

• Antlia H-alpha 3nm Pro Highspeed 2" filter in M48×0.75 threaded cell

Technical specifications

• filter type: narrowband, hydrogen H-alpha
• diameter: 2" (mounted)
• thread: M48×0.75
• 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: ≥ OD5 (300–1000 nm)
• recommended focal ratio: f/2.6–f/3.6
• applications: imaging of emission nebulae, planetary nebulae, Wolf–Rayet objects and supernova remnants
• substrate: optical-grade, single-layer, non-glued
• surface quality: scratch/dig 60/40 (MIL-O-13830)
• transmitted wavefront: λ/4 or better
• parallelism: <30″ (arcseconds)
• filter thickness (2" mounted version): 2.0 mm ±0.05 mm
• not recommended uses: visual observing, solar observing

Warning: NEVER look at the Sun through the Antlia H-alpha 3nm Pro Highspeed 2" filter. Ignoring this warning can cause permanent eye damage.