Astronomik SII 12nm CCD SC Rear Cell (2 / 24TPI) (SKU: 10216050 / 8h00br) all astro filters opinie

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Astronomik SII 12 nm CCD SC Rear Cell Filter (2" / 24TPI) (SKU: 10216050 / 8h00br) is a narrowband sulfur filter designed for imaging SII-emission nebulae. The SC Rear Cell version is made to mount directly to the rear thread of Schmidt-Cassegrain telescopes using the 2" / 24 TPI standard, placing the filter in the optical train right behind the OTA.

The filter significantly increases contrast between objects emitting at the sulfur lines 671.7 nm and 673.0 nm and the sky background. At the same time, it efficiently blocks common light pollution components: sodium (Na) and mercury (Hg) lamp lines, natural airglow, and most scattered moonlight. The result is a darker background and much stronger nebular detail.

With its narrow FWHM and high transmission, the filter passes essentially only the key SII emission lines while blocking nearly all other wavelengths from ultraviolet (UV) to infrared (IR).

At low light-pollution sites, the background signal is often limited by the sensor’s dark current rather than sky brightness. In such conditions, further reducing bandwidth does not necessarily reveal additional object detail.

Imaging with Astronomik narrowband filters

Astronomik narrowband emission-line filters are a powerful way to capture high-quality deep-sky images even under severe light pollution. An H-alpha filter is often the first choice, enabling detailed imaging of red emission nebulae even during full Moon. OIII filters expand your options by capturing greenish and bluish structures typical for planetary nebulae, star-forming regions, and supernova remnants.

Adding an SII filter completes the set and enables imaging in the HSO (H-alpha, SII, OIII) palette, often referred to as the “Hubble palette”, producing spectacular false-color emission-line results.

Differences between SII 4 nm, 6 nm and 12 nm filters

4 nm and 6 nm versions are ideal for very faint targets in star-rich Milky Way fields and are also recommended for extremely low-dark-current cameras or imaging from locations with extreme light pollution.

The 12 nm filters are designed for typical DSLR CMOS sensors and CCD cameras with normal or higher dark current. They are also often preferred for cameras with integrated guiding sensors, as they usually show more guide stars.

Astronomik MFR vs MaxFR coatings

Both MFR and MaxFR coatings provide excellent blocking from UV to IR, extremely high contrast, minimal stray light, no halos, and sharp stars.

MFR:
• 12 nm – f/3 to f/∞
• 6 nm – f/4 to f/∞
• 4 nm – f/4.5 to f/15

MaxFR is optimized for very fast optics:
• 12 nm – fully usable from f/1.7 to f/6 and about 85% of maximum transmission at f/1.4
• 6 nm – fully usable from f/2.2 to f/6 and about 90% of maximum transmission at f/2
• 4 nm – currently under development
Filters for even faster optical systems are available on request.

Technical specifications

• guaranteed transmission above 90% at both SII lines: 671.7 nm and 673.0 nm (for 12 nm / 6 nm / 4 nm)
• typical transmission: 96% (12 nm) and 93% (6 nm and 4 nm)
• mounting thread: SC Rear Cell 2" / 24 TPI
• glass thickness: 1 mm (except OWB Type 3 and XT filters)
• finely polished optical glass free of internal stress and bubbles
• extremely durable, scratch-resistant coating; fully resistant to humidity and aging
• Astronomik MFR coating
• parfocal with other Astronomik filters
• diffraction-limited performance
• optimized transmission ranges
• supplied in a durable protective filter box

Thanks to high-precision substrate manufacturing, Astronomik filters are parfocal and feature wedge errors far below common tolerances. Each filter undergoes strict quality control, and narrowband emission-line filters are additionally measured with a PerkinElmer spectrophotometer to verify compliance with published specifications.