Baader S-II Ultra-Narrowband Filter 4nm
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Vai al moduloThe Baader S-II Ultra-Narrowband Filter 4nm is the even narrower-band version compared to the standard Narrowband (6.5nm), designed for maximum possible contrast even under heavily light-polluted skies (Bortle 9/8/7/6).
What it's for
Linear filter with a 4nm FWHM passband, recommended for optical systems from f/10 to f/3.5. Compared to the standard Narrowband version, the narrower passband allows for even greater contrast, further reduces the apparent size of stars and reveals the finest details of emission nebulae — essential under heavy urban light pollution.
Baader CMOS-Optimized technology
The filter is coated with Reflex-Blocker™ treatment, which eliminates unwanted reflections even in the presence of auxiliary optics, and with Life-Coat™ technology: a hardened coating that does not flake, does not degrade and lasts the filter's entire lifetime even under the most extreme conditions. The edges are blackened all around, with a visual indicator on the front side for correct orientation during mounting. The filter is individually polished and coated, with no exposed coating edges.
Available formats
Available in 7 formats: 1¼" (31.8mm), 2" (50.8mm), 31mm, 36mm, 50.4mm, 50×50mm and 65×65mm.
Technical specifications
| Parameter | Value |
|---|---|
| Type | S-II Ultra-Narrowband |
| Central wavelength | 671.7 nm |
| Bandwidth (FWHM) | 4 nm |
| Recommended optical systems | f/10 to f/3.5 |
| Filter thickness | 2 mm |
| Coating | Reflex-Blocker™, Life-Coat™ |
| Brand | Baader Planetarium |
Who it's for
Ideal for astrophotographers working under heavily light-polluted skies who want the maximum possible contrast for S-II imaging, or for those who want to purchase the individual filters of the SHO palette separately to complete or replace an existing set. Compatible with filter wheels and most mono CMOS cameras.