Antlia Ultra Narrow Band 2.5nm SHO Filters
Antlia Ultra Narrow Band 2.5nm SHO FiltersAntlia Ultra Narrow Band 2.5nm SHO FiltersAntlia Ultra Narrow Band 2.5nm SHO FiltersAntlia Ultra Narrow Band 2.5nm SHO Filters

Antlia Ultra Narrow Band 2.5nm SHO Filters

£590.00✓ 2 year warranty


2x in stock shipped 1-2 working days

About this product

Model:  antlia_25nm_sho_ha
Part Number:  H-alpha 2.5nm Ultra 2

Antlia Ultra Narrow Band 2.5nm SHO Filters

The Antlia SHO 2.5nm Ultra series filters are made with quartz glass and undergo precisely controlled coating processes to ensure optimal performance. The 2.5nm Ultra series is designed with a FWHM (full width half maximum) of 2.5nm +0.3/-0.1nm and a transmission efficiency >93-95% at the Central Wavelength.

The quartz glass possesses an ultra-low thermal expansion coefficient with outstanding thermal and mechanical properties. When combined with advanced coating processes, these filters exhibit remarkable durability for imaging and research in the most challenging environmental conditions.

Compared to the 3nm Pro series, the 2.5nm Ultra series coated on quartz glass exhibits higher transmittance with Ha/SII≥95% and OIII≥93%. These filters are estimated to improve your images' signal by 20-30%. Additionally, the Ultra series boasts a narrower FWHM of 2.5nm+0.3/-0.1nm, resulting in an exceptionally high Signal-to-Noise Ratio for deep-sky photography.


  • High transmittance (Ha/SII≥95%, OIII≥93%) and narrow FWHM 2.5nm +0.3/-0.1nm to maximise contrast.
  • Flat-top spectrum minimises the loss in transmission due to the Centre Wavelength (CWL)-shift.
  • Out-of-band blocking specification is designed to OD5 (0.001%) to block interference from other wavelengths and minimise halos around bright stars.
  • Made of quartz glass for excellent durability and thermal stability, better fracture and scratch resistance, and improved coating resilience to cleaning.
  • Filters are resistant to scratches.
  • Identical filter thickness to existing standards and double-sided fine polishing, with utmost care for parfocality.
  • The SHO 2.5nm Ultra filters are recommended for use with optics with a Focus Ratio of ≥ f/3.5 for best optical performance.
  • 100% of production are scanned individually. All transmission and blocking (OD) data in the box are actual, measured spectra and transmission.
  • All Antlia filters are coated to the edge of the substrate, and unmounted narrowband filters are edge blackened to eliminate internal reflections from stray light.
  • 3-year warranty against delamination.

Filter Sizes

  • 1.25’’ (M28.5*0.6), 2’’(M48*0.75)*
  • Ultra-thin filter cell maximises clear aperture to minimise vignetting
  • Black Anodized Finish
  • Laser Engraving No Fading

* 1.25" not yet available


Not Recommended For:

Solar imaging

Nighttime visual observation


Serious eye damage will result if you fail to observe the warning.



FWHM 2.5nm +0.3/-0.1nm 2.5nm +0.3/-0.1nm 2.5nm +0.3/-0.1nm
Central Wavelength 656.3nm 672.4nm 500.7nm
Peak Transmission 95% 95% 93%
Blocking >OD5 >OD5 >OD5
Filter Thickness 2mm+/-0.05mm 2mm+/-0.05mm 2mm+/-0.05mm


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