Astronomik - OIII 12nm CCD Filter - 36mm Round Unmounted

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The Astronomik OIII CCD filter is a narrow band emission-line-filter for CCD photography.

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Product Description

Astronomik OIII-CCD 12nm Emission Line Filter - 36mm Round Unmounted

The Astronomik OIII CCD filter is a narrow band emission-line-filter for CCD photography. The filter lets the light of double ionized Oxygen of emission nebulae pass and blocks nearly the whole remainder of the spectrum.

The full width at half maximum (FWHM) of 12 nm is optimal, suitable for common CCD cameras and allows the use of very fast optics The optimal aperture ratio for the use of the filter is 1:3 to 1:15 with apertures of more than 6" (150mm). It should be noted that the filter has a transmission of up to 99%, which cannot be attained by stacking more narrow-band filters. A further note, which led to selecting the half width (FWHM), is the dark current of common CCD imagers. Exposures with a CCD cooled to -15°C are limited by the dark current of the CCD, even in large cities with a bright background. Another advantage of the 12 nm filter is the better availability of guiding stars for cameras with a built-in-autoguider (SBIG). If you use a very strong filter like our H-alpha 6nm filter you often won’t find a usable guidestar.

Together with the other three Astronomik emission-line filters you can do great color images even from very light polluted places 

The Astronomik OIII CCD increases the contrast between objects, in this case between the OIII emission line and the skyglow background. Our Astronomik OIII CCD completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when extremely bright aperture ratios of 1:2 and more come into play. The filter has a built-in IR-blocker up to 1150nm. You don’t need an additional IR-blocker with this filter.

When using the Astronomik OIII CCD filter together with the H-alpha, OIII CCD and the SII CCD filters you can obtain three-color images of emission line objects (gas nebulae) from locations with very strong light pollution. To do so, you would take an image in three different wavelengths, select each one as a color-channel in Photoshop and paste them together as one single color image.

If you plan to create color images from emission line data, a CLS CCD filter is a great choice for the Luminance channel The OIII CCD is also great for visual observation. If you plan to get filters for visual observation and for astrophotography get the CCD filter: You may use this filter visual as well as in front of you camera. The built-in IR blocker doesn’t disturb visual observation but you need an additional IR-blocker if you want to use the visual filter with your camera.

Astronomik 36mm OIII-CCD Filter (12nm) Features:

  • 95% transmission at 496nm (OIII)
  • 95% transmission at 501nm (OIII)
  • Full width at half maximum 12nm
  • Transmission from 494nm to 506nm
  • Parfocal with other Astronomik filters
  • Glass thickness: 1mm
  • Completely resistant against high humidity, scratches and aging effects
  • Diffraction limited, the filter will not reduce the optical performance of your telescope
  • Astronomik filters are delivered in a high-quality filter box
  • 10 Year Warranty




Transmission curve of an Astronomik Visual OIII filter. From left to right the dashed lines indicates the position of Hb (bleue), [OIII] doublet (green), Ha at 6563 A (red) and [SII] line at 6730 A (cyan).


Detail of the Astronomik Visual [OIII]  filter transmission curve.


Transmission curve of an Astronomik CCD [OIII] filter.


Detail of the Astronomik CCD [OIII] filter transmission. The bleue dashed line indicate the position of Hb line (at 4861 A). The Cyan dashed lines indicate the position of the [OIII] doublet at 5007 A (the most intense) and 4959 A.  This filter is not a pure oxygen filter, some light of neutral hydrogen is also transmitted.




Name Astronomik - OIII 12nm CCD Filter - 36mm Round Unmounted
Manufacturer Astronomik
Custom Stock Status Ships in 3-5 Days


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