Astronomik Narrowband 6nm Filters


Astronomik Narrowband 6nm Filters – Emission line filters ideal for imaging nebulae from light polluted skies.

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Astronomik Narrowband 6nm Filters – Photographic Emission line

*Please note: We can not ship Astronomik filters to Europe*

Full-Width-Half Maximum (FWHM): 6nm  – MFR Coating technique, usable with all optics up to f/4. Faster optics require the MAXFR line of narrowband filters.

  • H-alpha: Guaranteed Transmission of more than 90% at the H-alpha Line (656 nm), typical transmission of 96% at the H-alpha Line (656 nm)
  • OIII: Guaranteed Transmission of more than 88% at the OIII Line (501 nm), typical transmission of 92…95% at the OIII Line (501 nm)
  • SII: Guaranteed Transmission of more than 90% at both SII lines (671,7nm and 673,0nm), typical transmission of 94% at both SII lines (671,7nm und 673,0nm)

G HA 12nm u 6nm


G OIII CCD 12nm u 6nm


G SII CCD 12nm u 6nm

Quality aspects of the new Astronomik MFR Narrowband-Emission line Filters:

  • MFR Coating: The 12nm Filters can be used on all instruments up to f/3, the 6nm filters up to f/4. (Filters for faster optics are available upon request.)
  • 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! We have supplied parfocal filters for optical system as fast as f/1!
  • Coating: Astronomik filters are made of up to 130 layers which are coated on both sides of the substrate. These layers form the filter itself and act as a 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 it´s full performance and meet the specs at the point of shipping even after lot´s of years.
  • Integrated Blocking: All unwanted light is blocked in the whole spectral range from UV up to the IR! (You will not need an additional UV & IR-Blocker when imaging with the new Narrowband-Emission line Filters with MFR 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 do offer a 10 year guarantee on all of our filters. (Check some forums, we REALLY do so!)

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 enormous! You are investing your money for an accessory which will work in lot´s of years in the same ways 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!

Imaging with Narrowband-Emission line 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 kind of light pollution can be blocked very effective! Normally an H-alpha filter should be your first step into this amazing field of astrophotography! With an Narrowband H-alpha filter you will be able to take deep and contrasty images even wih very heavy light pollution or with the full moon high up in the sky!
If you look at other astrophotos, an H-alpha is the best choice for all nebulas glowing red! An OIII filters expands your imaging possibilities, as you are able to image all greenish/blueish structures. Planetary nebulas and star forming regions are great targets! The SII filters completes your HSO-set of filters. With these three filters you are able to process your images like the ones from the Hubble space telescope!
The h-beta filter is not available in a 6nm version, as this filter has nearly no meaningful application. To illustrate this, there are two images shown below: Both were taken with a unmodified Canon 650D. Even as the camera has a sensitivity of less than 10% at H-alpha, there is some signal und structure in the h-alpha image, while you cannot see anything on the image taken with an H-beta filter!

Operation of the filter:
The filter blocks all unwanted light from artificial light-pollution, natural airglow and moonlight. Especially light from High- and Low-Pressure Sodium and mercury lights and all lines of natural airglow are 100% blocked. The filter increases the contrast between the sky-background and objects glowing at the xx line at xy nm.

The orientation of the filter in the filter wheel does not matter. It does not change the optical performance.

Astronomik H-alpha filter MUST NOT BE USED for solar observation!

Which Full-Width-Half-Maximum is the best one for me? 12nm or 6nm?

The question which Full-Width-Half-Maximum (FWHM) is the “best”? A general “right” or “wrong” or “best” does not make any sense. -We would not offer both series if they were not needed.
When imaging from the city/suburb the images taken with DSLRs and most CCD cameras are limited by the dark current of the sensor and not by the brightness of the sky background. In this case you will not see fainter structures when using a 6nm filter instead of the 12nm version. Additional to that cameras with an integrated guiding sensor will get more stars for guiding with the 12nm filters!
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 very 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 milkyway!
To put it short: 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!



Additional information


1.25" (M28.5), threaded, 31mm, unmounted with protective cell / unthreaded, 36mm, unmounted with protective cell / unthreaded, 2" (M48), threaded, 50mm round, unmounted with protective cell / unthreaded, 50x50mm square, unmounted with protective cell / unthreaded


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