Skip to content

Astronomik OIII 12 nm CCD Filter - 31 mm Round - OIIICCD-31

shipping truck Free shipping
SKU: ASF-OIIICCD-31

Astronomik OIII 12 nm CCD Filter - 31 mm Round


  • This 12 nm OIII CCD Filter from Astronomik is designed specifically for astrophotography and comes in a round, 31 mm cell
  • Near complete transmission in the OIII line
  • FWHM bandwidth of approximately 12 nm
  • The ideal filter for capturing photos of planetary nebulae and the remnants of supernovae
  • Coatings protect remarkably well against scratching, aging, and humidity
  • This filter is diffraction limited and thus will not reduce your telescope's optical performance level
  • German-designed for supreme optical quality!
  • Best-suited for telescopes with a 6" aperture at minimum


More About the Astronomik 31 mm OIII 12 nm CCD Filter


This Astronomik OIII CCD Filter, a narrowband emission-line filter for CCD astrophotography, features a full width at half maximum (FWHM) of 12 nm. This is optimal for use with typical CCD cameras, enabling the use of extremely fast optics. This filter permits the light of double ionized oxygen from emission nebulae pass through while blocking close to the entire rest of the spectrum in the areas where the CCD is sensitive. The aperture ratio range ideally suited for this filter is 1:3 to 1:15 with apertures above 6" (150 mm). It should also be acknowledged that Astronomik O-III CCD Filters have an up to 99% transmission, a figure that cannot be attained by stacking extra narrowband filters. An additional note on the dark current of typical CCD imagers: exposures with a CCD cooled to -15°C are constricted by the CCD's dark current, even in large metropolitan areas with a heavily illuminated background. This directly influenced the 12 nm FWHM choice. A further benefit of this 12 nm filter is the easier availability of guiding stars for cameras that have an integrated autoguider.

Emphasizing the contrast between objects in the OIII emission line and the skyglow background, the Astronomik OIII CCD Filter offers complete suppression of emission lines from spurious light sources like mercury (Hg), sodium (Na), and airglow. Loss of transmission and chromatic distortions, which can be a problem with filters available from other manufacturers, are only an issue with Astronomik filters when excessively bright aperture ratios of 1:2 or more are in play. Since this filter has a built-in IR-blocker up to 1150 nm, an extra IR-blocker is not required.

Obtaining three-color images of emission line gas nebulae when imaging in heavily light polluted areas is possible if you use this Astronomik OIII CCD Filter in collaboration with the H-alpha and SII CCD filters. After capturing an image in three separate wavelengths, you can use Photoshop to select each as a color-channel, and combine them into a single color image. Diffraction limited, this filter will not have any negative influence on the optical performance of your telescope! All Astronomik filters come with a durable, high-quality plastic storage container.

Transmission Specifications


  • 99+% transmission for both of the OIII lines
  • Obstructs undesired wavelengths in other areas of the visible spectrum