Optolong SII CCD 12nm Narrowband Filter 31mm Unmounted for Astrophotography - Perfect for Deep Sky Imaging of Nebulae and Galaxies

The Sulfur II 12nm Narrowband Filter by Optolong works by transmitting a 12nm bandwidth of light centered on the 672nm wavelength, and reducing of wavelengths responsible for pesky light pollution. Wavelengths responsible for natural light pollution, or skyglow, are drastically reduced, as is artificial light pollution caused by high and low-pressure sodium vapor and mercury vapor lights. The result is a high contrast image that reveals objects glowing at 672nm, even under light polluted skies or when the Moon is at or near full. Use this filter with OIII and H-Alpha 12nm filters to get false color emission line images like the Hubble Space Telescope does.

A 12nm SII filter is recommended for cameras that have an integrated guiding sensor. You’ll have lots more guide stars to choose from with a 12nm filter as opposed to the extra-narrowband 6.5nm version. Like all Optolong filters that are designated as “CCD”, this S-II filter also blocks infrared wavelengths from 700nm to 1100nm so you don't need a separate IR-Cut filter.

The Optolong 36mm Unmounted SII 12nm Filter is made with Schott glass that has been multi-coated with an ion-assisted deposition technology to ensure scratch resistance and stability on the central wavelength or CWL. This 12nm SII filter is designed to be used in filter wheels that accept 36mm unmounted filters in a round format.

Quality Filter Materials:

• Schott B260 substrate material from Germany, 2.0mm thick

• Multiple layers of anti-reflection non-cementing coatings applied via electron-beam gun evaporation with Ion-assisted deposition

Optolong Filter Manufacturing Processes and Parameters

• Filter substrate is fine-optically polished to 1/4 wave and <30 parallelism over both surfaces

• Surface quality, according to MIL-O-13830, is 60/40

• 90% transmission at SII 672nm

• Infrared wavelength of 700-1100nm is cut off

• 0.1% transmission Hg at 435nm and 578nm

• 0.1% transmission Na at 589nm

• High-value transmission of pass-band and optical density of off-band is assured through Optolong’s planetary rotation system, a homogeneous and precise coating procedure

• Each filter comes with a plastic case with high-pressure EVA case lining

About Optolong

Optolong is the Astronomy Filters division of Yulong Optics, an optical filter design, and processing company out of Kunming, China that has provided filters for over 700 optical companies since 1999. All Optolong filters pass European Union RoHS requirements and have been certified by TUV Rheinland and Bureau Veritas.