Antlia H-Alpha 2.5 nm Ultra Filter 2" - Extra Narrowband Filter

Antlia Ultra Narrowband Filter with 2.5 nm Bandwidth

Antlia nebula filters offer extreme contrast. Thus, the astrophotographer achieves a very good result even with considerable stray light from cities or from the moon. Antlia guarantees a transmission of at least 95% (for the H-alpha filter) in the 1 nm range around the central passband. This makes the narrowband filters interesting also for fast telescopes and objectives. Even at an extreme focal ratio of f/3.5, there is only minimal transmission loss.

The quality features of Antlia narrowband filters at a glance:

High transmittance and narrowest bandwidth 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

Single substrate to eliminate internal reflections

Identical filter thickness to existing standards and double-sided fine polishing , with utmost care for parfocality

The SHO 2.5 nm Ultra filters are recommended for use in optics with a focus ratio of slower than 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

Superior optical reliability reduces post-processing of the image

Low-profile filter mount for better compatibility with filter wheels and drawers

Some detail about these 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 2.5 nm +0.3/-0.1 nm 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 2.5 nm +0.3/-0.1 nm, resulting in an exceptionally high Signal to Noise Ratio for deep sky photography.

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