Optolong deep sky S-II 6.5nm filter, unmounted round disk with D-36mm
Suitable for photographing weak emission nebulae in moonlight or strong light pollution, but also for narrowband imaging in the so-called "Hubble palette"
♦ narrow band line filter (<=7nm) for important nebula line
♦ preferred for CDD cameras with full frame transfer technology
♦ 2mm thick and therefore homofocal with many other Optolong filters
♦ Interference filter
♦ Frameless glass panel with a diameter of 36 mm
♦ optically polished
♦ Multi-layer hard coating - non-reflective and largely scratch resistant
Optolong S-II 6.5nm deep sky filter, 36mm diameter round disk
The 6.5nm SII CCD Extra Narrow Band Filter is designed for observing nebulae with a bandwidth of only 6.5nm and a central wavelength of 672nm, which corresponds to the emission line [S III]. Transmission at the other wavelengths is extremely low, particularly those radiating artificial light sources such as mercury vapor and both types of sodium vapor lamps, but also unwanted natural light emitted by neutral oxygen in the atmosphere (brightness of the sky).
Main use and properties
♦ Suitable for photographing weak emission nebulae in moonlight or when there is a lot of light pollution
♦ By combining H-alpha, OIII-CCD and SII-CCD, narrowband recordings can be made in the so-called "Hubble palette", such as the famous "Pillars of Creation" (M16, Eagle Nebula).
| Substrate: | High-quality optical glass from Schott |
| Thickness: | 2.0 mm |
| Surface Treatment: | Fine-optically polished |
| Surface Polish Quality: | 60/40 (Refer to MIL-O-13830) |
| Surface Quality: | 1/4 wavefront |
| Coating: | Muti-coated |
| Cell: | unmounted glass plate with 36 mm diameter |
| Typical transmission off-band: | 0.1% (OD3) |
| Centre wavelength [S II]: | 672 nm |
| FWHM [S II]: | 6.5 nm |
| Typical transmission [S II]: | 80% |
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