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).
||High-quality optical glass from Schott
|Surface Polish Quality:
||60/40 (Refer to MIL-O-13830)
||unmounted glass plate with 36 mm diameter
|Typical transmission off-band:
|Centre wavelength [S II]:
|FWHM [S II]:
|Typical transmission [S II]: