Antlia OIII Pro narrowband filter optimizes the FWHM (full width half maximum) to 3nmbandpass. As the bandwidth becomes narrower, the 3nm Pro narrowband filters enhance contrast of emission targets by lowering the unwanted background signal. Antlia OIII 3nm Pro filters are designed to deliver 85% transmission at the 500.7nm 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 Center Wavelength (CWL) shift. We guarantee T>85% 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 minimize interference from other wavelengths. Improved sharp cut off astrophotography 3nm Pro filters are designed to minimize halos around bright stars.

Application and Performance

High transmittance and smallest bandwidth to maximize contrast

Steep spectral profile minimizes halos around bright stars

A single substrate to eliminate internal reflections   

Narrowband Objects: OIII 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

Antlia narrowband Pro filters can be used down to F/3 systems with slight loss of signal

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

Superior optical reliability reduces post image processing

This filter is not suited to deep sky objects that do not contain OIII emissions.

Technical Specifications

Basic Substrate: Optical Substrate

Filter Thickness:   2mm+/-0.05mm for Dia36mm Unmounted

FWHM (Full width at half maximum): 3nm

CWL (Central Wavelength): 500.7nm

Peak Transmission: ＞85%

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

Warranty: 3-years against delamination

Not Recommended:

Solar Observing and imaging

Visual observation

DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS.

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

The Antlia SII 3.0nm filter is suitable for imaging SII emissions from nebulae, planetary nebulae and supernova remnants.

The 3.0nm bandwidth delivers a high transmission at a center wavelength of 671.6nm. The extreme narrowness in bandwidth enables astro-imaging from heavily light polluted locations and delivers improved contrast at darker sites. The filter effectively suppresses interference from other wavelengths, especially artificial mercury and sodium lamps.
Antlia narrowband filters are designed to bring out the faintest features in nebulosity by reducing the unwanted background frequencies. The narrower the filter, the better. Our SII filter is designed to deliver 90 % transmission at the 671.6nm line. The out of band blocking specification is rated OD3 (0.1%) which delivers an excellent signal to noise ratio and effective cut off rate to minimize interference from other wavelengths.
A sharp cut off rate is a very important performance index since it is designed to sharply attenuate off-band wavelengths. The result is that the Antlia SII filter delivers excellent contrast with extremely dark backgrounds whilst delivering a high transmission of the SII signal. The sharp cut-off also minimizes the effect of halos around bright stars.
In the production process, we use very strict quality control standards. Each filter is individually tested and scanned to ensure that the product meets our high-performance parameters. Our exacting attention to tolerances requires each substrate to have a uniform thickness that achieves no more + -0.05mm deviation from specification.

Application and Perfomance

Ultra-narrow 3.0 nm bandwidths, designed for astronomy imaging in both light polluted areas and at dark sites                                                                                                                             

Suitable for imaging of SII emission in nebulae, planetary nebulae and supernova remnants;

With the Ha, SII, OIII set of filters you are able to process your images to achieve the impressive Hubble color palette;

High transmission of typically 90% and sharp cut-off delivers an excellent boost in contrast for SII emitting objects;

All Antlia Narrowband filters are edge blackened to minimize interference from stray light;

This filter is not suited to deep sky objects that do not contain SII emissions. It can be used to image SII regions in galaxies and such images can be combined into LRGB images to better highlight the SII emitting regions of galaxies.

Technical Data

Schott optical substrate:

    1.25”, 2” mounted, 31mm,36mm dia (2mm+/-0.05mm)

    50mm dia，50*50mm，65*65mm square (3mm+/-0.05mm)

    Surface Quality: 60/40 (Refer to MIL-O-13830)

    2 sides fine-optically polished to ensure accurate 1/4 wavefront

    30 arcsec parallelism

Center-Wavelength of Antlia SII 3.0nm filter: 671.6nm

SII 671.6nm T＞90%, 90 % transmission at H-Alpha line at 656.3nm

OD3（0.1%）@ 300-1000nm

Both sides with multi-layer anti-reflection coating

Single / Non-glued substrate

Filter Cell (specifications for cell mounted filters only)

1.25” (M26*0.6)，2” (M48*0.75)

Ultra-thin filter cell to minimize vignetting by maximize possible clear aperture

Black Anodized Finish

Non-Fading Laser Engraving

Available Sizes

Mounted： 1.25” & 2” (2mm thickness)

Unmounted：Dia 31mm，Dia 36mm (2mm thickness)

Unmounted：Dia 50mm (3mm thickness)

Unmounted：50*50mm，65*65 square (3mm thickness)

Not Recommended

Solar Observing and imaging

Visual observation

IMPORTANT! DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS.

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

Chroma SII filters isolate the spectral emission of singly ionised sulfur atoms, also common in nebulae. Emission is at two lines occurring as a doublet, at 671.6 and 673.1 nm. This filter also separates sulfur emission from H-alpha emission (656.3nm).

About Chroma

Chroma Technology is an employee-owned company based in Vermont, USA. Chroma manufacture the highest quality astronomy filters with durable, sputtered hard coatings using single substrates of the best glass, eliminating the need for laminations. All primary filter coatings are applied on the front surface and anti-reflection coatings on the rear surface to prevent ghosting and to maximise transmission. Chroma astronomical filters are used worldwide in research and amateur applications. 

Highly precise and accurate, the passbands of these filters remain spectrally stable and do not drift in response to extreme temperature fluctuations or changes in humidity.

All filters may be used with focal ratios of f/4 or slower. For optics faster than f/4 then due to the spectral shift we recommend using the 5nm filters instead.

Features of the Chroma SII Filter

CWL: 672.4nm, Bandwidth: 3nm

• Durable sputter coatings
• Parallelism: <30 arcsec
• Thickness: 3.0 +/-0.05mm
• Filters designed for use with CCD and for f/4.0 or slower
• Transmitted wavefront better than 0.25 waves/inch
• No reflections leading to image distortions or ‘back reflections’

Chroma’s OIII filters isolate the 500.7nm primary emission line of doubly ionised oxygen. After H-alpha, this is the next most common emission when imaging nebulae.

About Chroma

Chroma Technology is an employee-owned company based in Vermont, USA. Chroma manufacture the highest quality astronomy filters with durable, sputtered hard coatings using single substrates of the best glass, eliminating the need for laminations. All primary filter coatings are applied on the front surface and anti-reflection coatings on the rear surface to prevent ghosting and to maximise transmission. Chroma astronomical filters are used worldwide in research and amateur applications. 

Highly precise and accurate, the passbands of Chroma filters remain spectrally stable and do not drift in response to extreme temperature fluctuations or changes in humidity.

All Chroma filters may be used with focal ratios of f/4 or slower. For optics faster than f/4 then due to the spectral shift, we recommend using 5nm filters instead.

Features of the Chroma OIII Filter

CWL: 500.7nm, Bandwidth: 3nm

• Durable sputter coatings
• Parallelism: <30 arcsec
• Thickness: 3.0 +/-0.05mm
• Filters designed for use with CCD and for f/4.0 or slower
• Transmitted wavefront better than 0.25 waves/inch
• No reflections leading to image distortions or ‘back reflections’

Chroma 3nm H-alpha filters are essential for imaging nebulae and other objects which are rich in ionised hydrogen. At 656.3nm, a narrow-band emission filter is required to separate H-alpha from the SII doublet (671.6nm and 673.1nm).

About Chroma

Chroma Technology is an employee-owned company based in Vermont, USA. Chroma manufacture the highest quality astronomy filters with durable, sputtered hard coatings using single substrates of the best glass, eliminating the need for laminations. All primary filter coatings are applied on the front surface and anti-reflection coatings on the rear surface to prevent ghosting and to maximise transmission. Chroma astronomical filters are used worldwide in research and amateur applications. 

Highly precise and accurate, the passbands of Chroma filters remain spectrally stable and do not drift in response to extreme temperature fluctuations or changes in humidity.

All Chroma filters may be used with focal ratios of f/4 or slower. For optics faster than f/4 then due to the spectral shift, we recommend using 5nm filters instead.

Features of the Chroma H-Alpha Filter

• CWL: 656nm, Bandwidth: 3nm
• Durable sputter coatings
• Parallelism: <30 arcsec
• Thickness: 3.0 +/-0.05mm
• Filters designed for use with CCD and for f/4.0 or slower
• Transmitted wavefront better than 0.25 waves/inch
• No reflections leading to image distortions or ‘back reflections’