Astronomik 6 nm H Alpha CCD Clip Filter for Canon EOS M Cameras

Astronomik Clip Filter for mirrorless APS-C Cameras of the Canon EOS M System

The Astronomik 6 nm H-alpha Filter is a narrow band-pass filter for hydrogen nebulae and can be inserted into the camera body within seconds.

Different from the 12 nm filter, contrast is enhanced strongly, helpful in heavily light polluted areas.

All transmission curves of the 6 nm filter are measured individually. Because of this procedure you can get the optimum filter for your telescope: If you place a direct order, please specify the focal ratio of your instrument, and we will select the best filter for your setup.

Alternatives:

If you plan to do (false-)color imaging with other emission line filters, you should get the filter with 12 nm FWHM. Images taken with filters with differing FWHM are very difficult to combine into the final image.

The Challenge:

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 camera’s 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-Filters are made of black anodized aluminum and laser-cut on state-of-the-art machines. They 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 operational!

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.)

Compatibility:

The clip filters for EOS M can be used with the models M1, M10, M3, M5, M6, M6MkII and M50.

Filter transmission curve:




♦ The horizontal axis is the wavelength in nanometers (nm). 400 nm is deep blue, at 520 nm the human eye senses green and at 600 nm red. At 656 nm is the famous "H-Alpha" emission line of hydrogen.
♦ The transmission in % is plotted on the vertical axis.
♦ The red line shows the transmission of the filter.
♦ Visual filters: The grey line in the background shows the relative sensitivity of the human eye at night. The maximum is at ~510 nm and drops to longer and shorter wavelengths. You can easily see, that you can´t see anything of the H-alpha line at night (even if you can during daylight!) The sensitivity at 656 nm is 0% at night!
♦ Photographic filters: The grey line in the background shows the sensitivity of a typical CCD sensor.
♦ The most important artifical emission lines are shown in orange. The artifical light pollution is dominated by see mercury (Hg) and sodium (Na), which are used in nearly all streetlights.
♦ The most important emission lines from nebulas are shown in green. The most important lines are from ionized hydrogen (H-alpha and H-beta), double ionized oyxgen ([O III]) and ionized sulfur ([S II]). The square brackets indicate that these lines are forbidden.

A short guide for selecting the right filter

Lots of customers are overwhelmed by the vast number of filters offered by Astronomik. Due to that they give you a short guide how to select the right filter for your application below:

Astronomik´s normal recommendation for the "First Filter" is the CLS filter. The CLS blocks all unwanted artifical light pollution and natural airglow and gives you a dark background in your images. When using this filter you may expose much longer than without, so you will be able to pick much fainter structures and objects. The filter is designed in such a way that all objects are given in their natural colors - they would look the same if your human eye would be much more sensitive!

The CLS is the fist choice for any applications like night-scape photography and time lapse movies!

Important: The standard CLS has no built-in IR-blocker. In case your camera has been modified for astrophotography, please take the CLS-CCD which has a built-in IR-blocker!

If you have to work under a heavily light polluted sky, the UHC is a good choice too. Its transmission curve is very tight. It gives you the light from the Hß, [O III], Hα and [S II] lines in one single exposure. The reduction of light pollution is much stronger than the CLS/CLS-CCD, but the filter will work for gas nebulas only - any galaxies and open or globular clusters are filtered out! You will get "false colors" with the UHC, not natural colors like with the CLS/CLS-CCD.

The UHC-E has a more broadband light transmission. Here stars are less strongly suppressed, helpful for nebulae with star clusters.

If you want to die deeper into astrophotography, you should think about emission line filters centered on OIII, H-alpha and SII, available either with 12 nm or even 6 nm bandwidth. With these filters you can do ultra-deep images even under the worst sky you can imagine plus the full moon high up in the sky. The emission line filters isolate the light from a very tight range of wavelengths, don´t get any color information. If you want to create color images (false color like images from the HST), you will need all three filters to mix the three channels into a final color image.

When using DSLR cameras without IR cut filter in astronomy, we recommend the UV-IR block filters of the L-1, L-2 and L-3 series to correct chromatic aberrations when using refractive optics (camera lenses, refractors). Depending on the color correction of your scope you may use a wider spectral window for the luminance data. The L1 filter has the widest spectral window, the L2 is about the same as our current L-Filter and the L3 is much narrower.

If you use an optical system that is more or less free of chromatic aberration you should get an L1 filter for your setup. For general use the L2 filter is well suited to most optical systems with a corrector, flattener or reducer in the optical train while the L3 filter is designed for users of refractors with a less-than-perfect color correction.

As protection against dust in DSLR cameras without IR cut filter, the MC clear glass filter is suitable. It blocks neither visible light nor UV or IR, but is parfocal with the other clip filters for Canon EOS-M cameras.

Especially made for planetary imaging are the ProPlanet IR pass filters. The IR light transmitted by them is less sensitive to air turbulence ("seeing"), which makes the images sharper, with increasingly longer wavelengths being increasingly less affected.

♦ 1 filter in plastic box