Astronomik H-alpha 12nm CCD Filter XT Clip-Filter EOS APS-C

Do you own a Canon EOS digital camera for astro-imaging? Then you have surely encountered the following problems:

• Large filters for large camera lens objectives are very expensive
• If you place a filter holder between your camera body and lens you loose the ability to focus to infinity
• For very fast (low f/ number) telescopes like the Vixen R200SS or the Takahashi Epsilon astrograph, a filter drawer or a filter wheel cannot be used since the distance to the corrector lenses would be changed.
• With long exposure times your cameras sensor chip is exposed to more dust

With the Astronomik Clip-Filter System you can take care of all of these problems at once!

The patented Astronomik Clip-Filter System is black anodized aluminum and laser-cut on state-of-the-art modern machines. It can be inserted within seconds directly into the EOS camera body. There are no changes necessary and all lens functions (focus, screen, image stabilization) remain functional!

Almost all Canon system lenses (with the exception of the EF-S series) and all M42 and T2 lens adapters, can be used with the Astronomik Clip-Filter System. The Clip-Filter System also acts as an outstanding dust shield, which prevents the possibility of dust settling on the sensor during long time exposure (The MC-Clear filter does not have a filter effect and only acts as a dust shield.)

List of compatible Canon EOS cameras:

Important: Not suitable are cameras offered before 2003 and all varieties of the Canon EOS 1D and EOS M.

The new Astronomik XT filters are designed to give you widefield-images with beautiful crisp and sharp stars right to the edge of the field.

Our Astronomik Clip filters are a popular and very well known tool among astrophotographers in the whole world. Sadly image quality was limited when using them with very short focal lengths to take widefield images: Even if the normal Astronomik filters are made of 1mm thick glas only, some wideangle lenses showed aberrations in the edge of the field of view when used with Clip-filters.

The new Astronomik XT filters are coated on an ultra-thin substrate with a thickness of 0.3mm only! Due to that the residual aberations are minimized and stars are crisp and sharp right into the corner of the image.

This extremely thin substrate is polished to the highest standards, free of internal strain and stress and suitable even for the most advanced imaging applications.

The XT filters are produced in the same way as the normal Astronomik filters: 100% scratch resistant, not sensitive to moisture or high humidity and no-ageing. Due to this the XT filters will have the same performance today and in many years in the future. To emphazise this you get a 10 year warranty on our filters!

Please note: Not all Astronomik filters are available as XT filters: Due to the huge amount of work to produce these ultra-thin filters, we are currently doing only a selection of filters, which are mostly used for widefield imaging. If you require a XT filter not listed below, please drop us a line.

This H-alpha Filter is suitable for imaging of Hydrogen nebulas from observation sites with light pollution and from dark sites as well. The contrast between an object glowing at 656nm and the background is increased enormous!

Due to the combination of the narrow bandwidth of 12nm and the high transmission of typically 96% the filter gives you an contrast boost, as all unwanted light from other wavelengths than 656nm is blocked form UV up to the IR. This results in an very dark background compared with any filters with a higher bandwidth
The FWHm of 12nm is optimized for typical DSLR cameras with CMOS sensors and CCD cameras with a normal/high dark current: With these cameras the background signal in images taken from heavily light polluted sites is dominated by the dark current of the sensor, not by fluy coming from light pollution. In this case a further reduction of FWHM does not improve the image, as the background will not get darker. Compared to the 6nm filters you have more stars in the field of view which gives you more guiding stars when working with an integrated/dual guiding chip!

Due to the new MFR coating technique you may use one single filter on all instruments up to f/3 without a significant reduction in performance.

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

Technical data of the filter:

• Guaranteed Transmission of more than 90% at the H-alpha Line (656 nm)
• Typical Transmission of 96% at the H-alpha Line (656 nm)
• Full-Width-Half Maximum (FWHM): 12nm
• 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/3
• 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

Imaging with Narrowband-Emissionline Filters
If you have to observe from light polluted sites (like most of us...), imaging with Narrowband-Emissionline filters is the best way to take great images, as all kind of light pollution can be blocked very effective! Normaly 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 meaningfull 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 artifical 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 H-alpha line at 656nm.

Tips and Hints for more applications:
Using the H-alpha filter together with OIII-CCD and SII-CCD filters you make produce false-color emission line images (HSO) in the same way as the Hubble-Space telescope. This is possible even from heavyly light polluted sites

Alternatives:
If want to image faint objects in starcrowded regions of the milkyway, propably using short focal lengths, the 6nm filter will be the better choice, as the number of stars is reduced by a factor of ~2. You should even take the 6n mversion if you have a camera with a low thermal current or if you have to observe from a really heavily light polluted site.