SII Antlia Ultra Narrowband 2.5nm filter

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

Antlia SHO 2.5nm Ultra series filters are made of quartz glass and benefit from precisely controlled coating processes to guarantee optimum performance. Their half-value width (FWHM) is 2.5nm +0.3/-0.1nm, with a transmission efficiency of between 92% and 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 with the Pro 3nm series, the filters in the Ultra 2.5nm series provide better transmission of emission lines. The Hα line at 656.3nm reaches ≥95%, the SII lines at 671.6nm/673.1nm ≥95%, and the OIII line at 500.7nm ≥92%. These filters can improve the signal in your images by 20 to 30%. What's more, their narrow bandwidth offers an exceptional signal-to-noise ratio for deep-sky astrophotography.

Application and performance

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.