Antlia H-a, SII and OIII 3nm Pro Highspeed Filter
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:
| Hydrogen-alpha | Oxygen III | Sulfur-II |
FWHM | 3nm | 3nm | 3nm |
CWL (Central Wavelength) | 657.5nm | 501.9nm | 673.6nm |
Peak Transmission | 90% | 90% | 90% |
Blocking | ≥OD5 @ 300-1000nm |
Filter Thickness | 2mm+/-0.05mm 2mm+/-0.05mm for 1.25”, 2” mounted, Dia31mm and Dia36mm unmounted 3mm+/-0.05mm for Dia50mm and square 50x50mm unmounted |
Sizes and MAP Prices:
Size | Minimum Advertised Pricing (MAP) |
Mounted: 2’’ | US$420 |
Unmounted: Dia36mm | US$325 |
Other sizes | Availability is to be confirmed |
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:
