Astronomik S-II 12nm Imaging Filter - Canon EOS XL Clip Filter
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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 12nm Astronomik Narrowband-Emissionline filters are better suited for use with typical DSLR cameras with CMOS sensors and CCD cameras with normal or high dark current or if you are observing from suburban or dark-sky locations. They are also the preferred choice for cameras with an integrated or dual guiding sensor, as they generally show more guiding stars compared to the 6nm filter.
In areas with little light pollution, the background signal in images is usually limited by the sensor's dark current rather than light pollution. Therefore, further suppression of the sky background by reduction of the FWHM does not bring out more details in the object.
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.
- 12nm MFR-coated filters can be used in all instruments with aperture ratios from f/3 to f/∞ without significant performance loss.
Clip-Filters for Canon EOS full-frame DSLR cameras
Since 2007 we offer our extremely popular Astronomik Clip-Filters. The complete range of Astronomik filters is available as Clip-Filters for the Canon EOS full-frame DSLR cameras.
The Astronomik Clip-Filters offer a number of practical advantages that make them an ideal choice for astrophotographers:
- Installing and removing the Astronomik Clip-Filter is very quick and easy and requires no extra tools or modifications to the camera body. They can be changed at any time, even at night.
- All lens functions, such as focus, aperture, and image stabilization remain fully functional.
- The Astronomik Clip-Filters are held securely in place without stressing the high-quality glass.
- The Astronomik Clip-Filters are designed and optimized for use with both standard camera lenses and telescopes.
Through the Astronomik Clip-Filters, we were able to solve several common issues faced by astrophotographers:
- Large filters for large camera lenses are very expensive.
- Using a filter holder between the camera body and the lens prevents focusing to infinity.
- For very fast telescopes (low f-number) like the Vixen R200SS or the Takahashi "Epsilon" astrograph, a filter drawer or filter wheel can not be used because the distance to the corrector lenses would be changed.
- Long exposure times lead to dust settling on the camera's sensor chip.
Due to the very tight bayonet and the limited space inside the camera, the Astronomik EOS XL Clip-Filters cause a minimal obstruction in the corners. But this can be easily corrected by flatfielding.
Use Astronomik filters for your Canon EOS full-frame DSLR camera and enjoy marvelous images with an ultra-light equipment!
Compatible Canon EOS full-frame DSLR cameras
| Model | Compatibility |
| Canon EOS-1D (all variants) | No |
| Canon EOS 5D | Yes, but no LiveView |
| Canon EOS 5D Mark II | Yes |
| Canon EOS 5D Mark III | Yes |
| Canon EOS 5D Mark IV | No |
| Canon EOS 5DS | No |
| Canon EOS 5DS R | No |
| Canon EOS 6D | Yes |
| Canon EOS 6D Mark II | No |
Technical Data
- Guaranteed transmission of more than 90% at both SII lines (671.7nm and 673.0nm)
- Typical transmission of 96% (12nm) at both SII lines
- Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)
- 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.