Antlia 4.5nm SII EDGE Astronomy Filter
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Antlia 4.5nm SII EDGE Astronomy Filter

£191.00✓ 2 year warranty


2x in stock shipped 1-2 working days

About this product

Model:  antlia_sii_4_5nm_125

Antlia 4.5nm SII EDGE Astronomy Filter

The Antlia SII EDGE narrowband filter optimises the FWHM (full width half maximum) to 4.5nm bandpass. The suppression of optical density (OD) 5 on unwanted wavelengths and the excellent transmittance characteristics found in the Antlia 3nm Pro series has been incorporated into the 4.5nm EDGE narrowband filters. The result is that these filters deliver superior SNR (signal to noise ratio) and better contrast in your images.

Antlia SII 4.5nm EGDE filters are designed to deliver high transmittance at the 671.6nm line that provides you with the maximum signal to reveal the faintest SII nebulae structures.

Conventional broader narrowband filters cause a heavy loss in transmission due to the strong Centre Wavelength (CWL)-shift. We guarantee T>90% within 1nm range of the centre bandwidth, which means that the SII 4.5nm EDGE narrowband filters can guarantee high transmittance for working with both long focal ratios and fast optical systems. Blue-shift data shows that Antlia 4.5nm EDGE 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.

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! 


  • 4.5nm FWHM SII filter - 671.6nm centre wavelength
  • High transmittance and smallest bandwidth to maximise contrast
  • Steep spectral profile minimises halos around bright stars
  • Suitable for imaging narrowband objects: SII 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

Purple 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)


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