Antlia 4.5nm Narrowband Sulfur II (SII) EDGE Filter - 1.25'' Mounted

Article number: SII4.5-125-Edge
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Antlia SII EDGE narrowband filter optimizes 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 Center Wavelength (CWL)-shift. We guarantee T>90% within 1nm range of the center 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.


Application and Performance:

High transmittance and narrow bandwidth to maximize contrast

Steep spectral profile minimizes halos around bright stars

A single substrate to eliminate internal reflections

Narrowband Objects: SII Emission Nebulae, Planetary, Wolf-Rayet Nebulae and Supernova Remnants

Use in light polluted areas and dark sites Extend imaging time when the moon is up

Antlia narrowband EDGE filters can be used down to f/3 systems with minimal loss of signal

All Antlia unmounted filters are edge blackened to eliminate internal reflections from stray light

Superior optical reliability reduces post image processing

This filter is only effective for deep sky objects that contain SII emissions


Technical Specifications:

Basic Substrate: Optical, Single / Non-glued substrate

Filter Thickness: 2mm+/-0.05mm for 1.25”

FWHM (Full width at half maximum): 4.5nm

CWL (Central Wavelength): 671.6nm

Peak Transmission: >90%

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


Warranty: 3-years against delamination


Spectrum Curve:

Antlia SII 4.5nm EDGE curve.jpg


Filter Ring: 1.25'' (M28.5*0.6)


Not Recommended:

Solar imaging

Night visual observation


Not Permitted:


Serious eye damage will result if you fail to observe the warning


When we design filters for astronomy imaging systems, we look at how they will work together with optical systems, carefully designing the out of band blocking rate, transmittance and band-pass parameters to achieve an optimum result. Each filter is individually tested and scanned by strict QC to ensure that the quality meets the high-performance parameters. The result is that Antlia is known for designing filters for astrophotography that achieve exceptional quality and performance parameters at affordable prices. We believe the price to performance ratio compares more favorably than similar premium filters in the market.

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