The Astronomik SII 12nm CCD Filter is suitable for imaging of SII-regions from observation sites with light pollution and from dark sites as well. The contrast between an object glowing at 672nm and the background is increased enormous!
Due to the combination of the narrow bandwidth of 6nm and the high transmission of typically 96% the filter gives you an enormous contrast boost, as all unwanted light from other wavelengths than 672nm is blocked form UV up to the IR. This results in an extremely dark background.
The FWHM of 6nm is matched to give you optimal performance with CCD and CMOS sensors with a very low dark current! The Astronomik SII 12nm CCD Filter is the best choice if you are observing from a heavily light polluted site or if you are imaging faint objects in star crowded regions of the milkyway.
Due to the new MFR coating technique you may use one single filter on all instruments up to f/4 without a significant reduction in performance.
Technical data of the filter:
- Guaranteed Transmission of more than 90% at both SII lines (671,7nm und 673,0nm)
- Typical Transmission of 94% at both SII lines (671,7nm und 673,0nm)
- Full-Width-Half Maximum (FWHM): 6nm
- perfect blocking of unwanted light from UV up to the IR
- parfokal with all Astronomik filters
- MFR Coating technique: Usable with all optics up to f/4
- Thickness of 1mm
- Not sensitive to moisture, scratch resistant, not aging
- opticaly polished substrate, striae-free and free of residual stresses
- High quality storage box
Astronomik MFR Narrowband-Emissionline Filters (OIII, SII, H-alpha, H-beta)
The new series of Astronomik MFR Narrowband-Emissionline Filters is perfectly matched to the requirements of astronomical Deep-Sky imaging. For the three most important emission lines of Oxygen (OIII), Hydrogen (H-alpha) and Sulfur (SII) you may select your filters either with 12nm or now a very narrow 6nm bandwidth. Astronomik utilises a completely new manufacturing process providing the best Off-Band blocking possible across the entire range of wavelengths from the UV through to IR! The benefit of this new design will be immediately obvious in your images – extremely high contrast, minimized stray light, no halos and needle-sharp stars.
Should I choose a 6nm or 12nm filter?
- 6nm filters are the perfect choice for capturing delicate detail in heavily light polluted skies. They are also appropriate with sensitive, low noise cameras under dark skies and for imaging faint detail in objects surrounded by rich star fields – and hence prone to overly saturated stars in the image. Best with f/3.75 to f/15 telescopes.
- 12nm filters are for photographers using typical DSLR cameras, inexpensive One Shot Colour CCD cameras or “noise limited” devices. The wider 12nm bandpass filters are also preferred generally when using cameras with an integrated guiding chip (behind the filters). Far fewer guide stars will be available at 6nm compared to 12nm. Best with f/2.8 telescopes and up.
What if my telescope has a fast f/ratio?
Unlike filters from many manufacturers, the transmission curve of the new Astronomik Narrowband-Emissionline filters are essentially free from bandpass shift when used with fast optical systems! While other manufacturers may sell special “High Speed” filters, or even require you having to buy different filters for each scope, this is not the case with the new Astronomik Narrowband-Emissionline filters with MFR coating. Your 6nm filters will be hunky dory on any telescope down as fast as f/4! (or f/3 with the 12nm FWHM filters).
How do I choose between OIII, SII, H-alpha, and H-beta?
The H-alpha filter is recommended as the filter of choice to begin exploring this amazing field of astrophotography. With a Narrowband 6nm H-alpha filter you will be able to take deep and contrasty images even with very heavy light pollution or with the full moon high up in the sky! A quick look at beautiful astrophotos will show an H-alpha filter is the best choice for all nebulae glowing with hues of pink to red. Think Orion Nebula, Eta Carina Nebula, Lagoon Nebula, Swan Nebula and so on and so forth. H-alpha light also appears in deep images of galaxies with active star formation regions showing up as beautiful pink knots in the spiral arms. In short – if you’re not incorporating H-alpha data into your images you must be bonkers.
An OIII filter (doubly ionized Oxygen) expands your imaging possibilities, as you are able to image all greenish/blueish structures. Planetary nebulas and star forming regions are great targets!
An SII filter (ionized sulphur – deeeeep in the red) completes your HSO set. With these three filters you are able to process your images like the ones from the Hubble space telescope (allowing compensation for atmospheric, or human-based error of course!).
The H-beta filter is not available in a 6nm version, as this filter has nearly no meaningful application. Used for very specific imaging targets such as the California Nebula, Horsehead Nebula, and some assorted planetary nebulas. Not recommended for beginners, and generally not widely used by most astronomers.