Astronomy Specialist



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The new Antlia S-II 3nm PRO ultra narrow-band it is the latest filter produced by Antlia. This filter boosts the contrast of emission and planetary nebulae, Wolf-Rayet nebulae and supernova remnants for professional results, even under a bright sky affected by light pollution.

The 3.0 nm 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 above 90% within 1nm of the centre bandwidth and the transmission off band is only 0.001%. 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.

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.

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.



Passing band 3 nm (FWHM)
Glass thickness

2.0 mm ±0.05

Optical flatness

1/4 λ (wavefront)

Bandpass transmission 90%
Off-band transmission <0.001% (OD5) @ 300-1000 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 size Unmounted 50 mm round
SKU 2" filter



Antlia Ultra Narrowband SII 3nm Pro filter transmission curve

SII 3nm filter transmission curve

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