Antlia Ultra Narrowband 2.5nm H-alpha filter

The Antlia H-a, SII and OIII 2.5nm Ultra filter series

The Antlia SHO 2.5nm Ultra series filters are made of quartz glass and feature precisely controlled coating processes to ensure optimal performance. Their full width at half maximum (FWHM) is 2.5 nm ±0.3 nm, with a transmission efficiency ranging from 92% to 95% at the center wavelength.

The quartz glass used has a very low coefficient of thermal expansion, with excellent thermal and mechanical properties. Combined with advanced coatings, these filters offer outstanding durability, even under extreme environmental conditions.

Compared to the Pro 3nm series, the filters in the Ultra 2.5nm series provide better transmission of emission lines. The Hα line at 656.3 nm achieves ≥95%, the SII lines at 671.6 nm and 673.1 nm achieve ≥95%, and the OIII line at 500.7 nm achieves ≥92%. These filters can improve the signal by 20 to 30% in your images. Additionally, their narrow bandwidth provides an exceptional signal-to-noise ratio for deep-sky astrophotography.

Technical specifications

Key features and applications

• High transmission (Hα/SII ≥95%, OIII ≥92%) and narrow bandwidth to maximize contrast
• Flat-top spectrum to limit losses due to CWL offsets
• OD5 out-of-band rejection (0.001%) to avoid interference and halos
• Made of quartz glass: excellent durability, scratch and break resistance
• Standard thickness, double polished for perfect fit
• Recommended for lenses with focal ratio ≥ f/3.5
• Each filter is measured individually and accompanied by its actual transmission curves.
• Edge-to-edge coating, black treatment on unmounted filters against internal reflections
• 3-year warranty against delamination

Filter mounts

• Standard Antlia ring: 1.25'' (M28.5*0.6), 2'' (M48*0.75)
• Ultra-thin cell for reduced vignetting
• Black anodized finish, unalterable laser engraving

Not recommended for :

• Solar observation
• Visual observation at night

Warning:

NEVER LOOK AT THE SUN WITH THESE FILTERS - This could result in serious eye damage.