Astronomik SII 12nm CCD MaxFR 31mm

MaxFR Astronomik photographic narrowband-emissionline filters for fast optical systems.

There is an ever-growing demand for filters suitable for extremely fast optical systems like Celestron´s RASA and the Epsilon Astrographs made by Takahashi.

Our novel MaxFR emission line filters are suitable up to very fast focal ratios. The new Astronomik MaxFR series of narrowband-emissionline filters is perfectly matched to the requirements of astronomical deep-sky imaging with fast optical systems. 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 6nm Bandwidth (FWHM).

MaxFR OIII-CCD filter
6nm and 12nm FWHM

MaxFR H-alpha-CCD filter
6nm and 12nm FWHM

MaxFR SIII-CCD filter
6nm and 12nm FWHM

Highest transmission:
Our new MaxFR filters are made in a completely new way, designed to work perfectly with fast optical systems. The built-in well-known MFR Coating technique gives you the best out-of-band blocking possible across the entire range of wavelengths from the UV up to IR! Your advantage of our new design is an extremely high contrast, minimized stray light, no halos and needle-sharp stars. The Astronomik MFR narrowband-emission line filters give you the best quality of data: The best start material to be processed into an awesome final image!

• For 12nm MaxFR filters this means unlimited usability from f/1.7 to f/8 and about 85% of the maximum transmission at f/1.4 as guaranteed.
  
• For 6nm MaxFR filters this means unlimited usability from f/2.2 to f/8 with about 90% of the maximum transmission at f/2 as guaranteed performance data.

For maximum contrast, the SII filter is carefully designed to block all light coming from H-alpha and NII (nitrogen).

Imaging with Narrowband-Emissionline Filters
If you have to observe from light-polluted sites (like most of us...), imaging with narrowband-emission line filters is the best way to take great images, as all kinds of light pollution can be blocked very effectively! Normally an H-alpha filter should be your first step into this amazing field of Astrophotography! With a Narrowband H-alpha filter, you will be able to take deep and contrasting images even with very heavy light pollution or with the full moon high up in the sky!
If you look at other astrophotographs, an H-alpha filter is the best choice for all nebula glowing red! An OIII filter expands your imaging possibilities, as you can image all greenish/blueish structures. Planetary nebulae and star-forming regions are great targets! The SII filter completes your HSO-set of filters. With these three filters, you can process your images like the ones from the Hubble Space Telescope!

Quality aspects of the new Astronomik MFR narrowband-emission line filters:

• MFR Coating: The 12nm Filters can be used on all instruments down to f/1.4, the 6nm filters down to f/2.
• High-Quality substrate: Astronomik filters are made with stress- and striae-free, optically polished glass. The filter itself is made of ultra-thin layers on this substrate!
• Parfocal filters: All Astronomik Filters are Parfocal! Due to the very small thickness tolerance, the focal plane is not shifted when changing filters!
• Coating: Astronomik filters are made of up to 170 layers, coated on both sides of the substrate. These layers form the filter itself and act as an Anti-Reflection Coating.
• Durability: Due to our coating technique, all Astronomik filters are highly scratch-resistant, not sensitive to moisture, and do not degrade when getting older. Every Astronomik filter will deliver its full performance and meet the specs at the point of shipping even after years.
• Integrated Blocking: All unwanted light is blocked in the whole spectral range from UV up to IR! (You will not need an additional UV & IR-Blocker when imaging with any of our new narrowband-emission line filters with coating!)
• Wide range of available sizes from 1.25" up to square 50mm x 50mm filters.
• Delivered in a high-quality protection & storage box.
• Due to our outstanding coating technique, we offer a 10-year guarantee on all of our filters.

You get the highest quality possible with every single Astronomik filter to be able to take perfect images with your instruments! Especially the filters against light pollution and the narrowband-emission line filters will expand your imaging possibilities enormously! You are investing your money for an accessory that will work for many years in the same way as it did when it was brand new. Due to our special coating technique, the filters do not degrade when getting older, and due to the new MFR coating, you will be able to use the filter on nearly all instruments!

Typical questions asked by customers looking for Narrowband-Emission line Filters:

• Which is the best full-width-half-maximum for me? 12nm or 6nm?

The question of which full-width-half-maximum (FWHM) is the "best" shows up often in emails or when talking to customers at fairs. A general "right," "wrong," or "best" does not make sense. We would not offer both series if they were not needed.
If you have a camera with an extremely low dark current and effective cooling, the 6nm filters will give you major advantages: Due to the stronger blocking of the background, you will be able to expose longer and get deeper images! All stars are tiny points; most faint stars do not show up anymore! This is a major advantage even for normal cameras, as you can take images of faint structures even in star-crowded regions of the Milky Way!
To put it shortly: 12nm Filters are the right choice for all DSLRs and dark-current limited cameras.
6nm filters are the best choice for observing sites with extremely strong light pollution, cameras with low dark-current, and when weak objects require the maximum contrast and star-reduction possible!

• How much is exposure time increased?

This question is asked quite often, and the answer is very simple: You don’t have to expose longer, but you MAY expose longer!
Due to the high transmission of approximately 100% at the center wavelength, nearly all emission line photons reach the sensor. So the number of "H-alpha-photons," for example, does not change significantly whether a filter is installed or not. But looking at the photons of other wavelengths, which we do NOT want to record, makes the filter's effect clear: The combination of excellent blocking of all unwanted light from UV to IR and the narrow bandwidth of the filters reduces all unwanted signals on the sensor! If you do a 30-sec exposure without any filters from a light-polluted urban observing site, your sky-background might already be very bright or even saturated. The same image taken with a Narrowband-Emission line filter will give you a perfect black background without any signal, and the signal from the object will be about the same. With this black background, you can expose longer, probably 30 min instead, to record fainter structures! So it’s not a "must," it’s a "can".

Selection of filters:
Please select the matching size for your setup and the FWHM to get a list of all available filters.