Antlia 3nm H-alpha (Ha) Pro Astronomy Filter
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Antlia 3nm H-alpha (Ha) Pro Astronomy Filter

£288.00✓ 2 year warranty


1x in stock shipped 1-2 working days

About this product

Model:  antlia_ha_3nm_31mm

Antlia 3nm H-alpha / Ha Pro Astronomy Filter

Antlia H-alpha Pro narrowband filter optimise the FWHM (full width half maximum) to 3nm bandpass. As the bandwidth becomes narrower, the 3nm Pro narrowband filters enhance contrast of emission targets by lowering the unwanted background signal. Antlia H-alpha 3nm Pro filters are designed to deliver 88% transmission at the 656.3nm line which provides you with the maximum signal and well defined nebulae structures.

Conventional broader narrowband filters cause a heavy loss in transmission due to the strong Centre Wavelength (CWL)-shift. Antlia guarantee T>88% within 1nm range of the center bandwidth, which means that the 3nm Pro narrowband filter can guarantee high transmittance for working with both long focal ratios and fast optical systems. Blue-shift data shows that Antlia 3nm Pro filters can be used with nearly all systems as fast as f/3 with minimal loss in emission signal and meets the requirements of fast optics like Hyperstar and RASA.

The out of band blocking specification is rated OD5 (0.001%) which delivers an excellent SNR (signal to noise ratio) and effective cut-off rate to minimise interference from other wavelengths. Improved sharp cut-off astrophotography 3nm Pro filters are designed to minimise halos around bright stars.

IMPORTANT: These filters are NOT designed for observing or photographing the Sun. DO NOT use these filters to observe or photograph the Sun. If you do it will result in permanent eye damage! 


  • 3nm FWHM Ha filter - 656.3nm centre wavelength
  • High transmittance and smallest bandwidth to maximise contrast
  • Steep spectral profile minimises halos around bright stars
  • Suitable for imaging narrowband objects: H-alpha Emission Nebulae, Planetary, Wolf Rayet Nebulae and Supernova Remnants
  • Use in light polluted areas and dark sites
  • Extends imaging time when the moon is up
  • Suitable for fast systems down to f/3 without loss of signal
  • Edge blackened to eliminate internal reflections from stray light
  • 2mm+/-0.05mm thickness for 1.25", 2" mounted, 31mm and 36mm unmounted
  • 3mm+/-0.05mm thickness for 50mm and 50x50mm unmounted
  • Fine-optically polished on both sides 

Transmission Chart

Blue Line - Represents the transmission curve of the filter.

The Major Emission Lines of Nebulae: H-α (656.3nm), H-β (486.1nm), OIII (495.9nm) and OIII (500.7nm)

The Major Emission Lines of Artificial Light Pollution: Hg / Mercury (435.8nm, 546.1nm, 577nm and 578.1nm), Na / Sodium (598nm, 589.6nm, 615.4nm and 616.1nm)



Basic Substrate: Schott optical substrate

Filter Thickness:   

2mm+/-0.05mm for 1.25", 2" mounted, 31mm and 36mm unmounted
3mm+/-0.05mm for 50mm and 50x50mm unmounted

FWHM (Full width at half maximum): 3nm

CWL (Central Wavelength): 656.3nmnm

Peak Transmission: >88%

Blocking: > 5 OD(0.001% out of band blocking) @ 300-1000nm

Surface Quality: S/D (scratch/dig)= 60/40 (Refer to MIL-O-13830)

Transmitted Wavefront: Lambda/4 or better.

Parallelism: less than 30 arcsec

Single / Non-glued substrate

Filter Ring:

1.25’’(M28.5*0.6) or 2’’(M48*0.75)

Ultra-thin filter cell to minimise vignetting

Black anodised finish Laser engraving

No fading

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