Antlia 2.5nm H-a Ultra Filter - 2'' Mounted

Article number: HA-2in-2.5nm-Ultra
Availability: More on the Way to us
Delivery time: More on the Way to Us
Size 2'' Mounted Price US$590
Brand Antlia Origin China
Filter detail Ha,SII,OIII    

Antlia H-a, SII and OIII 2.5nm Ultra Filter - Extra Narrowband filters   2" mounted

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 signal by 20-30% in your images. 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.


Technical Specifications:




Oxygen III


2.5nm +0.3/-0.1nm

2.5nm +0.3/-0.1nm

2.5nm +0.3/-0.1nm

CWL (Central Wavelength)




Peak Transmission






Filter Thickness





Sizes and MAP Prices


Minimum Advertised Pricing (MAP)

Mounted: 2’’

US$590.00 / pcs. US$1770 / SHO 2.5nm Ultra filters set

Other sizes

The release of 36mm unmounted is imminent



The main features and application:

- High transmittance (Ha/SII≥95%,OIII≥93%)and the narrow FWHM 2.5nm +0.3/-0.1nm to maximize contrast;

- Flat-top spectrum minimizes the loss in transmission due to the Center Wavelength (CWL)-shift;

- Out of band blocking specification is designed to OD5 (0.001%) to block interference from other wavelengths and minimize halos around bright stars;

- Made of quartz glass, excellent durability and thermal stability, better fracture resistance and scratch resistance, 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 in 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;

- Warranty: 3-years against delamination.



Spectrum Curves:

Ha 2.5nm ultra.jpgOIII 2.5nm ultra.jpgSII 2.5nm ultra.jpg



Filter Ring:

Antlia standard ring:1.25’’ (M28.5*0.6),2’’(M48*0.75)

Ultra-thin filter cell to minimize vignetting by maximize possible clear aperture

Black Anodized Finish

Laser Engraving No Fading



Not Recommended:

Solar imaging

Night visual observation



Not Permitted:


Serious eye damage will result if you fail to observe the warnin

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