Astronomy Specialist



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The Antlia S-II ultra narrow-band filter boosts the contrast of emission nebulae and supernova remnants for professional results, even under a bright sky affected by light pollution.

The 3.5nm band pass is only 1% of the entire visible spectrum, increasing the signal to noise ratio and delivering high contrast images and extremely dark backgrounds. To even further enhance the contrast, and suppress the stray light and internal reflections, Antlia applies edge-blackening coating on each filter.

The maximum transmission of the Sulphur II line (671.6 nm) is more than 90% and the transmission off band is only 0.1%. This is a value often undisclosed by other filter producers and it is critical to darken the sky background and minimise the halos around the stars.

Each filter is individually tested to ensure a high quality standard. The tight tolerance of the filters substrate assure a maximum deviance of ±0.05 from specifications making these filters parfocal.

The filter cuts off the ultraviolet and infrared light so there is no need to use the IR-cut filter.

DO NOT LOOK AT THE SUN WITH THE ANTLIA FILTERS. Serious eye damage will occur.

Antlia filters - Andrea Maggi

Crescent Nebula (NGC 6888) taken with Antlia filters by Andrea Maggi

Passing band 3.5 nm (FWHM)
Glass thickness

2.0 mm ±0.05

Optical flatness

1/4 λ (wavefront)

Bandpass transmission 88%
Off-band transmission <0.1% (OD3) @ 300-1050 nm
Coating Double-sided multilayer nano-coating
Surface quality 60/40 (in accordance with US military watch MIL-O-13830)
Parallelism 30"
Glass type Schott monolithic optical substrate (non glued)
Filter options Mounted 1.25", unmounted 36mm, mounted 2", unmounted 50mm
SKU 2" filter


Antlia filter absorbtion

SII filter transmission curve

Antlia SII filter absorbtion

SII filter absorption curve

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