Antlia SII 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 SII 3nm Pro filter is designed to deliver 88% transmission at the 671.6nm 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 show 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: 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
All Antlia narrowband Pro filters can be used down to F/3 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 SII emissions.
Specifications
Basic Substrate: Schott optical substrate
Filter Thickness：2mm+/-0.05mm for 1.25'' mounted
FWHM (Full width at half maximum): 3nm
CWL (Central Wavelength): 671.6nm
Peak Transmission: ＞88%
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.
When we design filters for astronomy imaging systems, we look at how they will work together with optical systems, carefully designing the blocking and band-pass parameters to achieve an optimum result. The out of band blocking rate is a very important performance index since it is designed to sharply attenuate off-band wavelengths. The result is that the Antlia SII 3nm Pro filter delivers excellent contrast with extremely dark backgrounds whilst delivering a high transmission of the SII signal. Such filters are more difficult to produce to a consistently high standard.
Each filter is individually tested and scanned to ensure that the quality meets the high-performance parameters. The end result is a filter that achieves excellent contrast but with a higher production cost. We believe the price to performance ratio compares more favorably than similar premium filters in the market.