Astronomik OIII 12nm CCD Filter - 31mm Round Mounted
The 31 mm Round OIII 12 nm CCD Filter
Mounted in Low Profile Non-Threaded Cell by Astronomik:
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.
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-inch (150 mm). It should be noted that the filter has a transmission of up to 99-inch, 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 Neg.15-degrees 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 6 nm filter you often won't find a usable guide star.
Together with our other three Astronomik emission-line filters you can do great false 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 1150 nm. 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.
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.
Now Mounted in Low Profile Non-Threaded Cell: Sometimes unmounted filters can be hard to handle. The smaller diameters, such as this 31 mm OIII filter, can be especially difficult to pick up and insert or remove from the filter wheel, and that can lead to possible damage as well as unwanted reflections from incorrectly installed filters. Astronomik has solved this problem by mounting their 31 mm and 36 mm filters in a low profile (3 mm) non-threaded cell. O-rings, washers, or spacers are no longer required to hold the filter in place, and because the cell is only 3 mm thick, it works well in all appropriately sized filter wheels. Mounted 31 mm and 36 mm Astronomik filters will also play nice with unmounted versions in the same carousel.
Astronomik OIII 12 nm CCD Filter - 31 mm Round Mounted Features:
- 95-percent transmission at 496 nm (OIII)
- 95-percent transmission at 501 nm (OIII)
- Full width at half maximum 12 nm
- Transmission from 494 nm to 506 nm
- Parfocal with other Astronomik filters
- Glass thickness: 1 mm
- Cell thickness: 3 mm
- 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, long lasting, filter box
OPT Product Number: AK-OIIICCD-31
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