The Astronomik H-alpha filter is a narrow band filter for CCD photography. The filter lets the H-alpha light 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 optimized for the use with common CCD cameras and allows the use of very fast optics. It should be noted that the filter has a transmission of up to 99%. Another advantage of the 12 nm filters is the availability of guiding stars for cameras with a built-in-autoguider (SBIG). If you use a very strong filter like our 6 nm filter, you often wont find a usable guidestar. An example for an exposure made at the rim a city can be found in "Reviews". The range of application extends from 1:2.8 to 1:15. 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. Main use: The Astronomik H-alpha CCD filter (12 nm version) increases the contrast between objects, in this case H-alpha emitting nebulae, and the skyglow background. This filter completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. Other uses: ♦ With using the [O III]-CCD and the [S II]-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 a color image. ♦ Achromatic refractors still have chromatic aberrations which make the star images bigger. With lines filters like this one, star images will shrink. ♦ The Astronomik 12 nm H-alpha filter may NOT be used for solar observation. ♦ If you plan to create color images from emission line data, our CLS-CCD filter is a great choice for the Luminance channel. Suitability: ♦ Visual observation (dark skies): Unsuitable ♦ Visual observation (urban skies): Unsuitable ♦ Film photography: Reasonable, but very long exposure times ♦ CCD photography: Very good, huge contrast enhancement at H II-emission nebulae ♦ DSLR photography (original): Good, reduced sensitivity in the H-alpha band ♦ DSLR photography (astro modified): Very good, huge contrast enhancement at H II-emission nebulae ♦ DSLR photography (MC modified): Very good, huge contrast enhancement at H II-emission nebulae ♦ Webcam / Video (Planets): Unsuitable ♦ Webcam / Video (Deep Sky): Good, good contrast enhancement with bright objects Technical Data: ♦ Transmission of over 97% with the H-alpha line (656 nm) ♦ Complete blocking from all disturbing wavelengths up to infrared ♦ Parfocal with other Astronomik filters ♦ Glass thickness: 1 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.
Item condition: used Item with possible small cosmetic deffect, but every function works perfect
Wichtiger Hinweis zur Mehrwertsteuer:
Dieses Angebot unterliegt mit Ausnahme der Versandkosten gemäß § 25a UStG der Differenzbesteuerung, weshalb auf den angebotenen Artikel keine Umsatzsteuer erhoben und ausgewiesen wird.
Delivery date : 2-3 days