Antlia 2.5nm Narrowband Sulfur II (SII) Ultra Imaging Filter - 36mm Round Unmounted
Stock count is accurate & shown in real time.
- This item is out of stock.
- Sign up for back-in-stock alerts to be notified when this item becomes available.
- This item is out of stock.
- We have no ETA from the manufacturer at this time.
- Sign up for back-in-stock alerts to be notified when this item becomes available.
Lower 48 States:
Orders over $50 ship free within the Lower 48 using a carrier and service we select based on your items and delivery location. Faster shipping options may be available at checkout.
U.S. Outside the Lower 48 (AK, HI, PR):
Free shipping on orders over $50 applies to many—but not all—items. Add items to your cart and enter your ZIP code to see available shipping options and any costs.
International Orders:
Free shipping does not apply to international orders. You’ll see available shipping options and costs during checkout. Some items can’t be shipped internationally due to size or manufacturer restrictions. Duties, taxes, brokerage fees, and tariffs are not included and are the customer’s responsibility.
IMPORTANT: Please read this important note below before buying Antlia narrowband filters. No returns will be accepted for Antlia narrowband filters exhibiting halos around bright stars as disclosed below.
Please note that some users may see halos around bright stars in images made with this filter. Such halos have been observed with filters from other leading manufacturers and in the previous generation of Antlia narrowband filters as well. These halos can be caused and/or made worse by other optical accessories in the imaging train, their relative positions, telescope design/optics, camera, software, or a combination thereof. In general, OIII filters seem to have a higher propensity to show halos compared to H-alpha or S-II filters, but in rare cases the latter filters can also exhibit faint halos around bright stars.
Antlia has made great strides in their coatings to minimize haloing of bright stars, but you may still observe this effect to some degree. See the sample OIII image below of Alnitak (magnitude 1.74) and IC434 in Orion (SkyRover 155mm Apo, ZWO 6200MM-P Camera, 20 min exposure) provided by Antlia. In most cases, haloing will not affect your image unless you have very bright stars in the field of view.
Please note we are unable to accept returns of any Antlia narrowband filters if you do observe this haloing effect in your images.
If you must ensure there are no detectable halos in your images, you may want to consider Astrodon or Chroma narrowband filters instead. These filters, however, cost two to three times as much as Antlia 3nm filters do. Antlia is being honest and upfront. They are the ones telling us about these halos, that their filters are great for the money but still not as good as Astrodon/Chroma, and pointing out that with this full disclosure, they will not accept returns. They are leaving it up to the customer to decide if this is good enough for them or not. We believe that for most imaging applications, Antlia filters continue to offer excellent value for astrophotographers and these continue to be among our top sellers.
The Antlia SII 2.5nm Ultra filter is made with quartz glass and undergoes precisely controlled coating processes to ensure optimal performance. The 2.5nm Ultra series is designed with a FWHM (full width half maximum) of 2.5nm +0.3/-0.1nm and a transmission efficiency >93-95% at the Central Wavelength.
The quartz glass possesses an ultra-low thermal expansion coefficient with outstanding thermal and mechanical properties. When combined with advanced coating processes, these filters exhibit remarkable durability for imaging and research in the most challenging environmental conditions.
Compared to the 3nm Pro series, the 2.5nm Ultra series coated on quartz glass exhibits higher transmittance with SII≥95%. These filters are estimated to improve signal by 20-30% in your images. Additionally, the Ultra series boasts a narrower FWHM of 2.5nm+0.3/-0.1nm, resulting in an exceptionally high Signal to Noise Ratio for deep sky photography.
Features:
- High transmittance (SII≥95%) and the narrow FWHM 2.5nm +0.3/-0.1nm to maximize contrast;
- Flat-top spectrum minimizes the loss in transmission due to the Center Wavelength (CWL)-shift;
- Out of band blocking specification is designed to OD5 (0.001%) to block interference from other wavelengths and minimize halos around bright stars;
- Made of quartz glass, excellent durability and thermal stability, better fracture resistance and scratch resistance, improved coating resilience to cleaning;
- Filters are resistant to scratches;
- Identical filter thickness to existing standards and double-sided fine polishing , with utmost care for parfocality;
- The SII 2.5nm Ultra filter is recommended for use in optics with a Focus Ratio of ≥ f/3.5 for best optical performance;
- 100% of production are scanned individually, all transmission and blocking (OD) data in the box are actual, measured spectra and transmission;
- All Antlia filters are coated to the edge of the substrate and unmounted narrowband filters are edge blackened to eliminate internal reflections from stray light;
- Warranty: 3-years against delamination.
Technical Specifications:
Sulfur-II
- FWHM: 2.5nm +0.3/-0.1nm
- CWL (Central Wavelength): 672.4nm
- Peak Transmission: 95%
- Blocking: ≥OD5
- Filter Thickness: 2mm+/-0.05mm
Filter Ring:
- None. 36mm round diameter, unmounted
Not Recommended:
- Solar imaging
- Night visual observation
DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS. Serious eye damage will result if you fail to observe the warning.
Other Information
- Country of Manufacture: China
The Antlia SII 2.5nm Ultra filter is made with quartz glass and undergoes precisely controlled coating processes to ensure optimal performance. The 2.5nm Ultra series is designed with a FWHM (full width half maximum) of 2.5nm +0.3/-0.1nm and a transmission efficiency >93-95% at the Central Wavelength.
The quartz glass possesses an ultra-low thermal expansion coefficient with outstanding thermal and mechanical properties. When combined with advanced coating processes, these filters exhibit remarkable durability for imaging and research in the most challenging environmental conditions.
Compared to the 3nm Pro series, the 2.5nm Ultra series coated on quartz glass exhibits higher transmittance with SII≥95%. These filters are estimated to improve signal by 20-30% in your images. Additionally, the Ultra series boasts a narrower FWHM of 2.5nm+0.3/-0.1nm, resulting in an exceptionally high Signal to Noise Ratio for deep sky photography.
Features:
- High transmittance (SII≥95%) and the narrow FWHM 2.5nm +0.3/-0.1nm to maximize contrast;
- Flat-top spectrum minimizes the loss in transmission due to the Center Wavelength (CWL)-shift;
- Out of band blocking specification is designed to OD5 (0.001%) to block interference from other wavelengths and minimize halos around bright stars;
- Made of quartz glass, excellent durability and thermal stability, better fracture resistance and scratch resistance, improved coating resilience to cleaning;
- Filters are resistant to scratches;
- Identical filter thickness to existing standards and double-sided fine polishing , with utmost care for parfocality;
- The SII 2.5nm Ultra filter is recommended for use in optics with a Focus Ratio of ≥ f/3.5 for best optical performance;
- 100% of production are scanned individually, all transmission and blocking (OD) data in the box are actual, measured spectra and transmission;
- All Antlia filters are coated to the edge of the substrate and unmounted narrowband filters are edge blackened to eliminate internal reflections from stray light;
- Warranty: 3-years against delamination.
Technical Specifications:
Sulfur-II
- FWHM: 2.5nm +0.3/-0.1nm
- CWL (Central Wavelength): 672.4nm
- Peak Transmission: 95%
- Blocking: ≥OD5
- Filter Thickness: 2mm+/-0.05mm
Filter Ring:
- None. 36mm round diameter, unmounted
Not Recommended:
- Solar imaging
- Night visual observation
DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS. Serious eye damage will result if you fail to observe the warning.
IMPORTANT: Please read this important note below before buying Antlia narrowband filters. No returns will be accepted for Antlia narrowband filters exhibiting halos around bright stars as disclosed below.
Please note that some users may see halos around bright stars in images made with this filter. Such halos have been observed with filters from other leading manufacturers and in the previous generation of Antlia narrowband filters as well. These halos can be caused and/or made worse by other optical accessories in the imaging train, their relative positions, telescope design/optics, camera, software, or a combination thereof. In general, OIII filters seem to have a higher propensity to show halos compared to H-alpha or S-II filters, but in rare cases the latter filters can also exhibit faint halos around bright stars.
Antlia has made great strides in their coatings to minimize haloing of bright stars, but you may still observe this effect to some degree. See the sample OIII image below of Alnitak (magnitude 1.74) and IC434 in Orion (SkyRover 155mm Apo, ZWO 6200MM-P Camera, 20 min exposure) provided by Antlia. In most cases, haloing will not affect your image unless you have very bright stars in the field of view.
Please note we are unable to accept returns of any Antlia narrowband filters if you do observe this haloing effect in your images.
If you must ensure there are no detectable halos in your images, you may want to consider Astrodon or Chroma narrowband filters instead. These filters, however, cost two to three times as much as Antlia 3nm filters do. Antlia is being honest and upfront. They are the ones telling us about these halos, that their filters are great for the money but still not as good as Astrodon/Chroma, and pointing out that with this full disclosure, they will not accept returns. They are leaving it up to the customer to decide if this is good enough for them or not. We believe that for most imaging applications, Antlia filters continue to offer excellent value for astrophotographers and these continue to be among our top sellers.
The Antlia SII 2.5nm Ultra filter is made with quartz glass and undergoes precisely controlled coating processes to ensure optimal performance. The 2.5nm Ultra series is designed with a FWHM (full width half maximum) of 2.5nm +0.3/-0.1nm and a transmission efficiency >93-95% at the Central Wavelength.
The quartz glass possesses an ultra-low thermal expansion coefficient with outstanding thermal and mechanical properties. When combined with advanced coating processes, these filters exhibit remarkable durability for imaging and research in the most challenging environmental conditions.
Compared to the 3nm Pro series, the 2.5nm Ultra series coated on quartz glass exhibits higher transmittance with SII≥95%. These filters are estimated to improve signal by 20-30% in your images. Additionally, the Ultra series boasts a narrower FWHM of 2.5nm+0.3/-0.1nm, resulting in an exceptionally high Signal to Noise Ratio for deep sky photography.
Features:
- High transmittance (SII≥95%) and the narrow FWHM 2.5nm +0.3/-0.1nm to maximize contrast;
- Flat-top spectrum minimizes the loss in transmission due to the Center Wavelength (CWL)-shift;
- Out of band blocking specification is designed to OD5 (0.001%) to block interference from other wavelengths and minimize halos around bright stars;
- Made of quartz glass, excellent durability and thermal stability, better fracture resistance and scratch resistance, improved coating resilience to cleaning;
- Filters are resistant to scratches;
- Identical filter thickness to existing standards and double-sided fine polishing , with utmost care for parfocality;
- The SII 2.5nm Ultra filter is recommended for use in optics with a Focus Ratio of ≥ f/3.5 for best optical performance;
- 100% of production are scanned individually, all transmission and blocking (OD) data in the box are actual, measured spectra and transmission;
- All Antlia filters are coated to the edge of the substrate and unmounted narrowband filters are edge blackened to eliminate internal reflections from stray light;
- Warranty: 3-years against delamination.
Technical Specifications:
Sulfur-II
- FWHM: 2.5nm +0.3/-0.1nm
- CWL (Central Wavelength): 672.4nm
- Peak Transmission: 95%
- Blocking: ≥OD5
- Filter Thickness: 2mm+/-0.05mm
Filter Ring:
- None. 36mm round diameter, unmounted
Not Recommended:
- Solar imaging
- Night visual observation
DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS. Serious eye damage will result if you fail to observe the warning.
Other Information
- Country of Manufacture: China
| Free Shipping Graphic | Free US Shipping |
|---|---|
| Hide Found a better Shipped Price on Frontend? | No |
Antlia 2.5nm Narrowband Sulfur II (SII) Ultra Imaging Filter - 36mm Round Unmounted