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Antlia 3nm Narrowband H-Beta Pro Filter - 2"
The Antlia 3nm Narrowband H-Beta Pro filter isolates the hydrogen-beta emission line at a central wavelength of 486.1nm with an extremely tight 3nm bandpass. This narrow window achieves a peak transmission of 88% while delivering greater than OD5 out-of-band blocking across the 300-1100nm range. It is built on a single, non-glued 2mm optical substrate with a transmitted wavefront of Lambda/4 or better, and all Antlia narrowband Pro filters can be used down to f/3 with minimal loss of signal.
3nm Bandpass at 486.1nm
The 3nm band is centred on the 486.1nm H-Beta line. As the bandwidth narrows, these filters enhance the contrast of emission targets by reducing unwanted background signal. Peak transmission is 88%.
The filter is only effective for deep-sky objects that contain H-Beta emission, and its targets are H-Beta emission nebulae; the California Nebula (NGC 1499) is a classic one. It can be used in light-polluted areas and at dark sites and extends imaging time when the moon is up.
>OD5 Blocking: Signal Purity from 300nm to 1100nm
Out-of-band blocking is rated greater than OD5 (0.001%) from 300nm to 1100nm. This ensures an excellent signal-to-noise ratio (SNR) and effective cutoff rates that minimize interference from other wavelengths.
Antlia adds that its optical reliability reduces post-processing.
Lambda/4 Optics on a Single Substrate
The filter is built on a single, non-glued substrate, which eliminates internal reflections. Its steep spectral profile minimizes halos around bright stars. This 2" filter is mounted; unmounted Antlia filters have blackened edges.
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Transmitted Wavefront: Lambda/4 or better.
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Parallelism: Less than 30 arcseconds.
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Surface Quality: 60/40 scratch/dig per MIL-O-13830.
Engineered for Fast Optics: Usable Down to f/3
In fast telescopes the steeper light cone shifts a narrowband filter's central wavelength toward shorter wavelengths (blue shift).
All Antlia narrowband Pro filters can be used down to f/3 with minimal loss of signal.
The Antlia 3nm Pro Series: Building a Full Narrowband Set
Antlia's 3nm Pro series covers H-alpha, SII, OIII and H-Beta, and these four narrow channels give a greater range of combinations in post-production.
A 3nm band passes less moonlight and skyglow around the line than a 7nm band, so the background is darker.
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How does the Antlia 3nm H-Beta Pro perform on the California Nebula (NGC 1499) with an f/4 scope?
The California Nebula is an H-Beta emission nebula, the kind of target this filter is made for. f/4 is slower than the f/3 limit given for the narrowband Pro filters.
Can I use the Antlia 3nm H-Beta Pro filter to image from my light-polluted backyard?
Yes. It can be used in light-polluted areas. The 3nm band and >OD5 blocking let only light close to the 486.1nm line through.
Why would I choose the Antlia 3nm H-Beta Pro instead of a more common H-alpha filter?
H-alpha is the stronger hydrogen line in most emission nebulae. H-Beta adds a fourth channel; the four 3nm Pro channels give a greater range of combinations in post-production.
What does the >OD5 blocking on the Antlia 3nm H-Beta Pro filter mean for my images?
OD5 blocking means that light outside the filter's 3nm bandpass is attenuated to 0.001% of its original intensity. It is rated from 300nm to 1100nm and ensures an excellent signal-to-noise ratio.
Is the Antlia 3nm H-Beta Pro filter safe for solar viewing or visual use?
No. Do not look at the Sun with this filter. Solar imaging and night visual observation are both listed as not recommended.
What is the benefit of the single-substrate design in the Antlia 3nm H-Beta Pro?
The single, non-glued substrate eliminates internal reflections.
Will the Antlia 3nm H-Beta Pro filter cause halos around bright stars?
The sharp cutoff of the 3nm Pro filters is engineered to reduce halos around bright stars, and the steep spectral profile minimizes them. Very bright stars can still show some halo.
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| Filter Type |
H-Beta Narrowband (3nm Pro series) |
| Central Wavelength (CWL) |
486.1nm |
| Bandpass (FWHM) |
3nm |
| Peak Transmission |
88% |
| Blocking Range |
300-1100nm |
| Blocking Depth |
>OD5 (0.001%) |
| Recommended F-Ratio |
Usable down to f/3 with minimal loss of signal |
| Filter Size |
2" Mounted (M48x0.75 Threads) |
| Filter Thickness |
2mm +/-0.05mm |
| Substrate |
Optical, single / non-glued |
| Surface Quality |
60/40 (per MIL-O-13830) |
| Transmitted Wavefront |
Lambda/4 or better |
| Parallelism |
< 30 arcseconds |
| Usage Warning |
Not recommended for solar imaging or night visual observation. Do not look at the Sun with this filter directly. |
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Antlia 3nm H-Beta Pro filter, 2" mounted
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Antlia 3-year warranty against delamination.
