Baader O-III CMOS Optimised Super-G 9nm Filter
Baader O-III CMOS Optimised Super-G 9nm FilterBaader O-III CMOS Optimised Super-G 9nm FilterBaader O-III CMOS Optimised Super-G 9nm FilterBaader O-III CMOS Optimised Super-G 9nm Filter

Baader O-III CMOS Optimised Super-G 9nm Filter

£77.00✓ 2 year warranty


Out of stock due 10-15 working days

About this product

Model:  baader_2961550
Part Number:  2961550

Baader O-III CMOS Optimised Super-G 9nm Filter

This O-III filter is designed for observing and photographing those gas nebulae in which doubly ionised oxygen fluoresces – i.e. primarily for planetary nebulae and supernova remnants. With a FWHM of only 9 nm and equipped with the CMOS-optimised coating technology, it darkens the sky background and thus also blocks stray light much better than its 10 nm predecessor. However, the narrower FWHM is not the most important improvement; it is the significantly better blocking sides of the O III wavelength, as well as even steeper transmission slopes and a broad plateau in the transmission range. With a transmission of 97% for the emission line at 500.7 nm, practically all the nebula light passes through the filter. At the same time, this filter can be used photographically for almost any focal ratio from f/1.8 to f/12 without passing any light of the H-beta line. This makes the Super-G filter ideal for use in high-light pollution areas.

Super-G filter: The filter has the same thickness as the 1.25″/2″ Baader LRGB filters. In the transmission range of the normal green filter (490-580nm), there are no emission lines other than OIII; the RGB blue filter already covers H-Beta at 486 nm. So, when using the 9 nm O-III filter instead of the standard RGB green filter, emission nebulae are consequently emphasised much more strongly, while the stars appear fainter. This makes it suitable for use as a “super G filter”.

Photographic use: The 9 nm O-III filter can be used photographically on all telescopes, especially with a DSLR or an astronomical OSC colour camera. It offers all the advantages of the CMOS-optimised Baader filters, such as Reflex-Blocker™ coating against reflections, plano-optical polishing and age-resistant Life-Coat™ coating. For monochrome cameras, we recommend the even stronger Narrowband (6,5 nm) and Ultra-Narrowband (4 nm) filters, which are available specially adapted for different aperture ratios. For this comparatively broadband 9 nm filter, preshifting is not necessary at focal ratios faster than f/4, thus it can be used at all focal ratios.


  • Increased contrast, matched for typical CMOS quantum efficiency and s/n ratio
  • Reflex-Blocker™ coatings, for the largest ever freedom from halos, even under most adverse conditions concerning aux-optics
  • Identical filter thickness to existing standards, with utmost care for parfocality
  • Blackened edges all around, with filter-lead-side-indicator in the form of a telescope-sided black outer rim, to additionally eliminate any reflection due to light falling onto the edge of a filter, making additional front masks obsolete
  • Each filter is coated individually, with a sealed coating edge (NOT cut out of a larger plate with coatings left exposed, read more)
  • Life-Coat™: evermore hard coatings to enable a non-ageing coating for life – even in a most adverse environment
  • It can be used as a “Super-G filter” replacement for RGB photography. While regular G-filters suffer from bad seeing due to air turbulences, the narrow range of 9 nm passes less thermal noise, i.e. sharper images. Nevertheless, the transmission window is large enough not to be considered a pure narrowband filter.



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