Antlia PRO Ha, SII, OIII Ultra Narrowband Highspeed filter set, 3 nm (36 mm, unmounted)

Antlia's SHO 3nm Pro Highspeed Filters are further optimized for high-speed imaging systems by pre-shifting the center wavelength. This specially-optimized version will provide significantly SNR (Signal to Noise Ratio) for the fast telescopes with focal ratio between f/2.6 and f/3.6 than the standard 3nm Pro version.

The optical light path of a telescope is cone-shaped, which creates an angle, and the center wavelength of the interference filter will shift toward shorter (blue) wavelengths as the angle of incidence((AOI) increases; the greater the angle， the greater the shift. The amount of beam deviation depends on the refractive index and the thickness of the substrate. The blue shift data by the simulation indicates that at a focal ratio of f/2.6, the angle of incidence of the light cone is 10°and its bandwidth shift 2.2nm to shorter wavelengths. Therefore, the Highspeed 3nm Pro narrowband filters are designed to be pre-shifted by 1.2nm towards the longer (red) end in order to compensate for the Blueshift and ensure high signal acquisition by telescopes with fast focal ratios.

Blueshift data simulation Figure:

Using these highspeed SHO 3nm Pro narrowband filters for the telescopes with focal ratio between f/2.6 and f/3.6 shows much stronger and more contrasted in astronomy imaging compared to the standard Pro version.

For optics f-ratios slower than f/3.6, the standard 3nm Pro filters are highly recommended. Meanwhile, if you use optics faster than f/2.6, the 4.5nm EDGE filters are the good choice.

Technical Specifications:

The main features and application

• - High transmittance Ha/SII/OIII＞90% and 3nm bandwidth to maximize contrast
• - Antlia narrowband Pro Highspeed filters can be used with focal ratio f/2.6-f3.6 systems with minimal loss of signal
• - Improved sharp cut-off astrophotography 3nm Pro series filters are designed to minimize halos around bright stars
• - 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
• - A single substrate to eliminate internal reflections
• - Narrowband Objects: 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
• - All Antlia unmounted narrowband Highspeed filters are edge blackened to eliminate internal reflections from stray light
• - Superior optical reliability reduces post image processing
• - Basic Substrate: Optical, Single / Non-glued substrate
• - 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

Filter Ring:

• Antlia standard ring:1.25’’ (M28.5*0.6)，2’’(M48*0.75)
• Ultra-thin filter cell to minimize vignetting by maximize possible clear aperture
• Black Anodized Finish
• Laser Engraving No Fading

Not Recommended:

• Solar imaging
• Night visual observation

Not Permitted:

• DO NOT LOOK AT THE SUN WITH THIS FILTER!!
• Serious eye damage will result if you fail to observe the warning.

Spectrum Curves:

The Antlia Pro narrowband filter optimizes the FWHM (full width half maximum) to 3nm bandpass. As the bandwidth becomes narrower, the 3nm Pro narrowband filters enhance contrast of emission targets by lowering the unwanted background signal. Antlia 3nm Pro filters are designed to deliver 88% or higher for Ha and SII, and 85% or higher for OIII 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>88% 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:

• Ultra-narrow 3.0 nm bandwidths, designed for astronomy imaging in both light polluted areas and at dark sites；
• Suitable for imaging of H-Alpha 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;
• With the Ha and OIII filters these can be used to achieve great narrowband results using the Bi-Color process;
• High transmission of typically 90% and sharp cut-off delivers an excellent boost in contrast for 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 Ha emissions. It can be used to image Ha regions in galaxies and such images can be combined into LRGB images to better highlight the Ha emitting regions of galaxies.
• Extends imaging time when the moon is up

Technical Data:

• Basic Substrate: Schott optical substrate
• Filter Thickness:   2mm+/-0.05mm for up to 2" and 3mm for 50mm unmounted
• FWHM (Full width at half maximum): 3nm
• CWL (Central Wavelength): 656.3nmnm
• Peak Transmission: ＞88% for Ha and SII, ＞85% for OIII
• 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