The Antlia 3nm Pro SHO Narrowband Filter Set combines three 2" mounted filters—Sulfur II, H-alpha, and Oxygen III—for high-contrast monochrome astrophotography and complete SHO image acquisition.
Each filter isolates one important nebular emission line through an ultra-narrow 3nm FWHM bandpass: SII at 671.6nm, H-alpha at 656.3nm, and OIII at 500.7nm. Capturing these wavelengths separately gives astrophotographers the data needed to create SHO Hubble-palette images, natural-looking narrowband blends, and other custom color mappings.
OD5 out-of-band blocking from 300–1000nm strongly suppresses broadband skyglow, artificial light pollution, and unwanted wavelengths. By reducing background brightness while maintaining high transmission at each target emission line, the Antlia 3nm Pro filters improve separation between faint nebular structure and the surrounding sky.
This three-filter set is intended primarily for cooled monochrome CMOS or CCD cameras used with a 2" filter wheel, filter drawer, or other M48-compatible holder. It is the standard Antlia 3nm Pro version, not the separately optimized 3nm Pro Highspeed version.
- Three-filter SHO set
- 3nm FWHM
- 2" mounted
- M48 × 0.75
- OD5 blocking
- Monochrome imaging
Antlia 3nm Pro SHO Filter Set Features
Complete SII, H-alpha and OIII Set
Collects the three individual emission channels required for SHO narrowband imaging and Hubble-palette processing.
Ultra-Narrow 3nm Bandpasses
Each filter uses a 3nm FWHM passband to isolate its target wavelength and increase nebula-to-background contrast.
OD5 Out-of-Band Blocking
Blocking greater than OD5 from 300–1000nm suppresses off-band light to 0.001% transmission or less.
High Emission-Line Transmission
Published minimum transmission is greater than 88% for SII and H-alpha and greater than 85% for OIII.
2" Mounted Filter Cells
Black-anodized, low-profile cells use standard M48 × 0.75 threads for compatible 2" filter wheels, drawers, and holders.
Reflection-Controlled Construction
Steep spectral cutoffs and single, non-glued optical substrates are designed to reduce unwanted reflections and halos.
What Each SHO Filter Captures
SII · Sulfur II
671.6nm center wavelength · 3nm FWHMRecords emission from singly ionized sulfur. SII is often the faintest of the three channels and is commonly mapped to red in an SHO Hubble-palette image.
H-alpha · Hydrogen-alpha
656.3nm center wavelength · 3nm FWHMCaptures hydrogen emission that forms much of the visible structure in many emission nebulae. H-alpha is commonly mapped to green in an SHO palette.
OIII · Oxygen III
500.7nm center wavelength · 3nm FWHMIsolates emission from doubly ionized oxygen, often revealing high-excitation regions, shells, and filaments. OIII is commonly mapped to blue in an SHO palette.
Antlia SHO Filter Set and Transmission Curves
View the complete 2" mounted set and the SII, H-alpha, and OIII 3nm Pro transmission-curve images. Select a thumbnail or use the arrows to browse.
01 / 04
Complete 2" Mounted SHO Set
Three separate 3nm Pro narrowband filters for SII, H-alpha, and OIII imaging with a monochrome astronomy camera.
02 / 04
SII 3nm Pro Transmission Curve
The SII filter is centered at 671.6nm with a 3nm full width at half maximum.
03 / 04
H-alpha 3nm Pro Transmission Curve
The H-alpha filter is centered at 656.3nm with a 3nm full width at half maximum.
04 / 04
OIII 3nm Pro Transmission Curve
The OIII filter is centered at 500.7nm with a 3nm full width at half maximum.
Best Targets for Antlia 3nm SHO Filters
Excellent Narrowband Targets
- Emission nebulae and HII regions
- Planetary nebulae
- Supernova remnants
- Wolf-Rayet nebulae and shells
- Faint filaments containing SII, H-alpha, or OIII emission
Not Intended for Broadband Imaging
- Natural-color galaxy imaging
- Reflection nebulae
- Open or globular star clusters
- Dark nebulae recorded through broadband starlight
- Targets without meaningful SII, H-alpha, or OIII emission
Light pollution and moonlight: The 3nm passbands and OD5 blocking can maintain strong emission-nebula contrast under substantial artificial light pollution and can extend useful imaging time when the Moon is present. They do not remove every gradient, and results still depend on target position, sky conditions, exposure, and calibration.
Standard 3nm Pro Focal-Ratio Compatibility
This listing is for Antlia’s standard 3nm Pro filters. Antlia recommends the standard version for optical systems slower than approximately f/3.6. It can be used near f/3, but a blue shift in the passband may reduce emission-line transmission.
For systems around f/2.6–f/3.6, Antlia’s separately sold 3nm Pro Highspeed filters are optimized for the steeper light cone. For optics faster than approximately f/2.6, Antlia generally recommends its wider 4.5nm EDGE filters. Because HyperStar and RASA systems vary in focal ratio, choose the filter version based on the actual optical speed of your system.
How the SHO Filter Set Is Used
Capture Each Channel
Use a monochrome camera to record separate SII, H-alpha, and OIII exposure sequences through the corresponding filters.
Calibrate and Integrate
Calibrate each channel with appropriate darks, flats, and bias or dark-flat frames, then register and integrate the data.
Map and Combine
For a traditional Hubble palette, map SII to red, H-alpha to green, and OIII to blue, then balance and process the combined image.
SII, H-alpha and OIII Filter Specifications
| Filter | Emission line | Center wavelength | FWHM | Published minimum transmission |
|---|---|---|---|---|
| SII | Singly ionized sulfur | 671.6nm | 3nm | >88% |
| H-alpha | Hydrogen-alpha | 656.3nm | 3nm | >88% |
| OIII | Doubly ionized oxygen | 500.7nm | 3nm | >85% |
Antlia 3nm Pro SHO Set Specifications
| Product type | Three-filter SHO narrowband astrophotography set |
|---|---|
| Included filters | SII 3nm Pro, H-alpha 3nm Pro, and OIII 3nm Pro |
| Mounted size | 2" / 50.8mm class |
| Filter-cell thread | M48 × 0.75 |
| Filter thickness | 2.0mm ±0.05mm |
| Substrate | Single, non-glued optical substrate |
| Out-of-band blocking | Greater than OD5 from 300–1000nm; 0.001% transmission or less outside the passband |
| Surface quality | 60/40 scratch-dig |
| Transmitted wavefront | λ/4 or better |
| Parallelism | Less than 30 arcseconds |
| Primary camera compatibility | Monochrome CMOS and CCD astronomy cameras |
| Recommended optical speed | Standard 3nm Pro version; best suited to systems slower than approximately f/3.6 |
| Manufacturer warranty | Three years against coating delamination |
| Starizona SKU | ANTLIA-3NM-SHO-PRO-SET-2 |
Frequently Asked Questions
What does SHO mean in astrophotography?
SHO stands for Sulfur II, Hydrogen-alpha, and Oxygen III. In the traditional Hubble-palette mapping, SII data is assigned to red, H-alpha to green, and OIII to blue.
Is this Antlia SHO set intended for monochrome or color cameras?
It is designed primarily for monochrome CMOS or CCD cameras. A monochrome sensor records the full available signal through each individual filter. The filters can transmit light to a one-shot-color camera, but the camera’s Bayer matrix makes separate SHO acquisition less efficient.
Can I use the standard Antlia 3nm Pro filters with HyperStar or RASA?
Compatibility depends on the system’s actual focal ratio. This standard set is best suited to optics slower than about f/3.6. For systems around f/2.6–f/3.6, use Antlia’s 3nm Pro Highspeed filters; for still faster systems, Antlia generally recommends the 4.5nm EDGE series.
Are the three Antlia filters parfocal?
All three filters share the same nominal 2.0mm optical thickness, which helps reduce focus changes. For critical imaging—especially with fast optics, temperature changes, or long sessions—automatic refocusing by filter is still recommended.
Why choose 3nm filters instead of wider narrowband filters?
A 3nm passband rejects more off-band light than a wider filter, producing a darker background and stronger contrast on emission-line targets. The tradeoffs are tighter focal-ratio requirements and, depending on the target and camera, potentially longer exposure or integration requirements.
Does this set include LRGB filters or a filter wheel?
No. This product includes only the three 2" mounted narrowband filters: SII, H-alpha, and OIII. LRGB filters, filter wheels, and filter drawers are sold separately.
Can these filters be used for visual observing or solar imaging?
No. The Antlia 3nm Pro SHO filters are intended for deep-sky astrophotography and are not designed for conventional visual observing or as solar filters.
What’s Included
- Antlia SII 3nm Pro filter — 2" mounted
- Antlia H-alpha 3nm Pro filter — 2" mounted
- Antlia OIII 3nm Pro filter — 2" mounted