Astronomik OIII CCD 12nm Passband Filter 1.25-Inch
Astronomik 1.25-Inch OIII CCD 12nm Passband Filter for CCD Photography
Mounted filter in 1.25" cell ( M28.5mm x 0.5mm)
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 where the CCD is sensitive.
Astronomik have re-designed all of their photographic filters. Since the end of 2008 they are shipping their new "Halo-Free" filters.
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 our 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 togther 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, our 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.
- Visual observation (dark skies): Very good, huge contrast enhancement at O III-emission nebulas
- Visual observation (urban skies): Very good, huge contrast enhancement at O III-emission nebulas
- Film photography: It depends, very long exposure time
- CCD photography: Very good, huge contrast enhancement at O III-emission nebulas
- DSLR photography (astro modified): Very good, huge contrast enhancement at O III-emission nebulas
- DSLR photography (MC modified): Very good, huge contrast enhancement at O III-emission nebulas
- DSLR photography (original): Very good, huge contrast enhancement at O III-emission nebulas
- Webcam / Video (Planets): Unsuitable
- Webcam / Video (Deep Sky): Reasonable, if light pollution is a big problem and OIII Objects are beeing observed
- 95% transmission at 496nm (OIII)
- 95% transmission at 501nm (OIII)
- transmission from 494nm to 506nm
- full width at half maximum 12nm
- Parfocal with other Astronomik filters
- Glass thickness: 1mm
- Diffraction limited, the filter will not reduce the optical performance of your telescope!
- Completely resistant against high humidity, scratches and aging effects
- Astronomik filters are delivered in a high-quality, long lasting, filter box
How to read the above chart?
* The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
* The transmission in % is plotted on the vertical axis.
* The red line shows the transmission of the filter.
* Visual filters: The grey line filled with grey in the background shows the relative sensitivity of the human eye at night. The maximum is at ~510nm and drops to longer and shorter wavelengths. You can easily see, that you can´t see anything of the H-alpha line at night (even if you can during daylight!) The sensitivity of the eye at 656nm is 0% at night!
* Photographic filters: The grey line in the background shows the sensitivity of a typical CCD sensor.
* The most important emission lines from nebulas are shown in green. The most important lines are from ionized Hydrogen (H-alpha and H-beta) and double ionized oyxgen (OIII) .
* The most important artifical emission lines are shown in orange. The artifical light pollution is dominated by mercury (Hg) and sodium (Na), which are used in nearly all streetlights.
The major emission lines of artifical light pollution:
| Hg 435,8nm | Hg 546,1nm | Hg 577,0nm |
Hg 578,1nm | | Na 589,0nm | Na 589,6nm |
Na 615,4nm | Na 616,1nm |
The major emission lines of nebulas:
H-β 486,1nm | OIII 495,9nm | OIII 500,7nm |