Astronomik Sulfur-II / S-II 6nm Imaging Filter - 31mm 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.
The Astronomik SII filter is ideal for imaging nebulae showing sulfur emissions from both light-polluted and dark observation sites. It significantly enhances the contrast between objects emitting light at 671.7nm and 673nm (SII lines) and the sky background. The Astronomik SII filter completely filters out the emission lines from high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps, as well as all lines of natural airglow and most of the distracting moonlight. For particularly high-contrast results, the Astronomik SII filter is optimised to prevent H-alpha light from passing through.
With a narrow bandwidth of either 12nm or 6nm and high transmission rates, the filter effectively blocks all unwanted light from wavelengths other than 671.7nm and 673nm from ultraviolet (UV) to infrared (IR).
Difference between Astronomik 12nm and 6nm filters
The choice between 12nm and 6nm Full-Width-Half-Maximum (FWHM) filters depends on your imaging conditions and camera type. There is no universal "best" option - each FWHM serves a specific purpose.
The 6nm Astronomik Narrowband-Emissionline filters are ideal for imaging faint objects in star-crowded regions of the milky way, as they typically halve the number of stars in the image compared to the 12nm filter. They are also suitable if you have a camera with very low dark current or if you are observing from a location with extreme light pollution.
Difference between Astronomik MFR and MaxFR coating
Both the Astronomik MFR and MaxFR coatings give you the best out-of-band blocking over the entire wavelength range from UV to IR, extremely high contrast, minimized stray light, no halos and needle-sharp stars.
- 6nm MFR-coated filters can be used in all instruments with aperture ratios from f/4 to f/? without significant performance loss.
Size of filter
Astronomik filters come in a wide range of standard sizes, both mounted and unmounted, to suit various optical setups and cameras.
This filter is a filter with a protective ring for filter wheels without screw thread. The glass thickness is 1mm, the mechanical thickness is 3mm, the diameter is 31mm.
Technical Data
- Guaranteed transmission of more than 90% at both SII lines (671.7nm and 673.0nm)
- Typical transmission of 93% at both SII lines
- Glass thickness: 1mm
- Finely polished optical glass, free of any striae, residual stresses, and bubbles
- Extremely scratch-resistant and durable coating
- Completely resistant against high humidity and aging effects
- Astronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)
- Parfocal with other Astronomik filters
- Diffraction-limited
- Optimized spectral windows
- Delivered in a high-quality, long-lasting filter box
Due to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated.
All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures.
Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.
Useful Resources
Filter Cell Specifications
Unlike other filter manufacturers, Astronomik mounts their round filters in unthreaded cells.
D = Filter Cell Diameter = 31 mm / 1.22 in
T = Total Filter/Cell Height = 3.5 mm / 0.14 in
S = Glass Substrate Thickness = 1 mm / 0.04 in
CA = Clear Aperture = 27.7 mm / 1.09 in
Other Information
- Country of Manufacture: Germany
The Astronomik SII filter is ideal for imaging nebulae showing sulfur emissions from both light-polluted and dark observation sites. It significantly enhances the contrast between objects emitting light at 671.7nm and 673nm (SII lines) and the sky background. The Astronomik SII filter completely filters out the emission lines from high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps, as well as all lines of natural airglow and most of the distracting moonlight. For particularly high-contrast results, the Astronomik SII filter is optimised to prevent H-alpha light from passing through.
With a narrow bandwidth of either 12nm or 6nm and high transmission rates, the filter effectively blocks all unwanted light from wavelengths other than 671.7nm and 673nm from ultraviolet (UV) to infrared (IR).
Difference between Astronomik 12nm and 6nm filters
The choice between 12nm and 6nm Full-Width-Half-Maximum (FWHM) filters depends on your imaging conditions and camera type. There is no universal "best" option - each FWHM serves a specific purpose.
The 6nm Astronomik Narrowband-Emissionline filters are ideal for imaging faint objects in star-crowded regions of the milky way, as they typically halve the number of stars in the image compared to the 12nm filter. They are also suitable if you have a camera with very low dark current or if you are observing from a location with extreme light pollution.
Difference between Astronomik MFR and MaxFR coating
Both the Astronomik MFR and MaxFR coatings give you the best out-of-band blocking over the entire wavelength range from UV to IR, extremely high contrast, minimized stray light, no halos and needle-sharp stars.
- 6nm MFR-coated filters can be used in all instruments with aperture ratios from f/4 to f/? without significant performance loss.
Size of filter
Astronomik filters come in a wide range of standard sizes, both mounted and unmounted, to suit various optical setups and cameras.
This filter is a filter with a protective ring for filter wheels without screw thread. The glass thickness is 1mm, the mechanical thickness is 3mm, the diameter is 31mm.
Technical Data
- Guaranteed transmission of more than 90% at both SII lines (671.7nm and 673.0nm)
- Typical transmission of 93% at both SII lines
- Glass thickness: 1mm
- Finely polished optical glass, free of any striae, residual stresses, and bubbles
- Extremely scratch-resistant and durable coating
- Completely resistant against high humidity and aging effects
- Astronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)
- Parfocal with other Astronomik filters
- Diffraction-limited
- Optimized spectral windows
- Delivered in a high-quality, long-lasting filter box
Due to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated.
All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures.
Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.
The Astronomik SII filter is ideal for imaging nebulae showing sulfur emissions from both light-polluted and dark observation sites. It significantly enhances the contrast between objects emitting light at 671.7nm and 673nm (SII lines) and the sky background. The Astronomik SII filter completely filters out the emission lines from high- and low-pressure sodium (Na)- and mercury (Hg)-vapor lamps, as well as all lines of natural airglow and most of the distracting moonlight. For particularly high-contrast results, the Astronomik SII filter is optimised to prevent H-alpha light from passing through.
With a narrow bandwidth of either 12nm or 6nm and high transmission rates, the filter effectively blocks all unwanted light from wavelengths other than 671.7nm and 673nm from ultraviolet (UV) to infrared (IR).
Difference between Astronomik 12nm and 6nm filters
The choice between 12nm and 6nm Full-Width-Half-Maximum (FWHM) filters depends on your imaging conditions and camera type. There is no universal "best" option - each FWHM serves a specific purpose.
The 6nm Astronomik Narrowband-Emissionline filters are ideal for imaging faint objects in star-crowded regions of the milky way, as they typically halve the number of stars in the image compared to the 12nm filter. They are also suitable if you have a camera with very low dark current or if you are observing from a location with extreme light pollution.
Difference between Astronomik MFR and MaxFR coating
Both the Astronomik MFR and MaxFR coatings give you the best out-of-band blocking over the entire wavelength range from UV to IR, extremely high contrast, minimized stray light, no halos and needle-sharp stars.
- 6nm MFR-coated filters can be used in all instruments with aperture ratios from f/4 to f/? without significant performance loss.
Size of filter
Astronomik filters come in a wide range of standard sizes, both mounted and unmounted, to suit various optical setups and cameras.
This filter is a filter with a protective ring for filter wheels without screw thread. The glass thickness is 1mm, the mechanical thickness is 3mm, the diameter is 31mm.
Technical Data
- Guaranteed transmission of more than 90% at both SII lines (671.7nm and 673.0nm)
- Typical transmission of 93% at both SII lines
- Glass thickness: 1mm
- Finely polished optical glass, free of any striae, residual stresses, and bubbles
- Extremely scratch-resistant and durable coating
- Completely resistant against high humidity and aging effects
- Astronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)
- Parfocal with other Astronomik filters
- Diffraction-limited
- Optimized spectral windows
- Delivered in a high-quality, long-lasting filter box
Due to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated.
All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures.
Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.
Useful Resources
Filter Cell Specifications
Unlike other filter manufacturers, Astronomik mounts their round filters in unthreaded cells.
D = Filter Cell Diameter = 31 mm / 1.22 in
T = Total Filter/Cell Height = 3.5 mm / 0.14 in
S = Glass Substrate Thickness = 1 mm / 0.04 in
CA = Clear Aperture = 27.7 mm / 1.09 in
Other Information
- Country of Manufacture: Germany
| Product Status | new |
|---|---|
| Free Shipping Graphic | Free US Shipping |
| Hide Found a better Shipped Price on Frontend? | No |
Astronomik Sulfur-II / S-II 6nm Imaging Filter - 31mm Round Unmounted