Astronomik OIII 12nm CCD Filter SC Rear Cell (2" / 24TPI)

Astronomik OIII CCD-Filter SC Rear Cell (2" / 24TPI) - ANK_OIIICCD-SCT

Het Astronomik OIII CCD filter is ontworpen voor CCD fotografie van gas en planetaire nevels. Door de smalle bandbreedte op de OIII lijn (501 nm) levert dit filter een zeer grote verhoging van het contrast, zelfs onder slechte waarneemomstandigheden. Dankzij de bandbreedte van 13nm levert dit filter een transmissie van 97%. Een waarde die ondenkbaar is bij nog smalbandigere filter.

Een OIII filter maakt vaak het verschil of dat zwakke supernova restant of zwakke planetaire neveltje wel of niet wordt vastgelegd. Dit filter blokkeert al het licht buiten de OIII golflengte en met name straatlantaarnlicht (Hg en Na) en de IR golflengten (hier is een CCD het meest gevoelig voor) worden niet doorgelaten.

Het filter kan gebruikt worden bij openingsverhoudingen tussen F2, 8 en F15 dankzij de hoge transmissie (97%) . Bijkomend voordeel hiervan is dat er gebruik gemaakt kan worden van de autoguide functie van dezelfde camera waarmee het object wordt vastgelegd (bijvoorbeeld bij de duurdere SBIG camera's) .

Erg interessant is om opnamen gemaakt door het OIII filter te combineren met opnamen gemaakt door SII en H-alpha filters. Dit biedt de mogelijkheid om drie kleuren opnamen te maken vanuit zeer lichtvervuilde gebieden!

Dankzij de hoge kwaliteit van het optisch glas geeft het Astronomik OIII filter speldepuntjes als sterren.

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.

We have re-desgined all of our photographic filters. Since the end of 2008 we are shipping our new "Halo-Free" filters. read more...

The full width at half maximum (FWHM) of 12nm 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 12nm 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!

Main use

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.

Other uses

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.

Suitability

• 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 (original) : 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
• 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)
• 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, long lasting, filter box