SII filter: The narrowband S-II 7nm filter passes light at 672nm wavelength with a bandpass of 3nm which is designed for nebula fotography.
It is suitable for most emission nebulae, planetary nebulae and supernova remnants.
f you want the look of Hubble Space Telescope (HST) images, such as the famous “Pillars of Creation” (the Eagle Nebula, Messier 16), then the next filter to consider adding to your collection after H-a and OIII is the SII (es-two) or sulfur filter. The SII filter, like H-a, is a deep red filter near 672 nm. H-a, OIII and SII filters provide that Hubble look for many emission nebula. Again, tri-color narrowband imaging with these three filters can be done with the moon up, so your equipment is not sitting dormant for several weeks.
Line filter with 4 nanometre half-width, recommended for optical systems from f/3.4 to f/2.3
Baader's CMOS-optimised filters are characterised by:
- increased contrast
- narrower half-widths (FWHM)
- Reflex Blocker™ coatings for maximum insensitivity to retro reflection from nearby auxiliary optics, even under the most adverse conditions
- FWHM carefully designed for each filter category to enable 1:1:1 exposures, matched to typical CMOS quantum efficiency and signal-to-noise ratio
- Identical filter thickness to existing standards, with the utmost care taken to ensure homofocality
- Blackened edges all around, with filter front indicator in the form of a black outer edge on the front to additionally prevent any reflection from light falling on the filter edge
- Each filter is individually precision-polished and coated, with a sealed coating edge (NOT cut from a larger plate with exposed coating edges)
- Life-Coat™: even harder coatings to enable an age-resistant coating with an unlimited service life – even in the most adverse environments
This new CMOS-optimised filter generation is designed to become the new standard in amateur astronomy.
