Astronomik OIII 6 nm CCD Filter - XL Clip Filter for Canon EOS R and RP

Astronomik XL Clip Filter for mirrorless Full-frame Cameras Canon EOS R and RP

This filter is suitable for photographing OIII regions from artificially light polluted areas or outside the city. The contrast between OIII light and the sky background is enormously increased.

The OIII CCD filter extremely increases the contrast between gas nebulae and sky background. The narrow FWHM combined with high transmission in the OIII lines region increases contrast strongly compared to more broadband filters.

The useful application range extends over a focal ratio of 1:4 to 1:15, the filter can be inserted into the camera body in seconds.

The 6 nm 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 Milky Way.

How it works

The filter blocks all unwanted light from artifical light-pollution, natural airglow and moonlight. Especially light from high and low pressure sodium and mercury vapor lamps and all lines of natural airglow are 100% blocked. The filter increases the contrast between the sky background and objects glowing at the more intensive OIII line, as not only the weaker line, but also a larger part of the disturbing continuum are suppressed.

Alternatives

The 12 nm filter is interesting if you want to capture more stars, for example from an embedded star cluster. The number of stars in the image is typically doubled.

Compatibility

Canon cameras EOS R/R5/R5/RP/Ra (the latter can show strong reflections around bright stars)

Not compatible with Canon RF 35 mm f/1.8 IS MACRO lens.

Application

Mounting the Astronomik EOS R XL Clip Filter:

Mounting the Astronomik EOS R Clip Filter is very easy: You don´t need any tools and filters may be changed even at night without any problems.

Remove the lens and take the Clip Filter from its box. Insert the Clip Filter into the body and push it in with two fingers, until it rests neatly. Re-install the lens and your camera is ready for imaging!

Removing the Astronomik EOS R XL Clip Filter:

A small hook is included for easy disassembly of the clip filter. Insert the hook into the slot in the clip filter and pull the clip filter forward out of the body.

Grab it with two fingers and put it back in the storage box. After attaching the lens, the camera can be used as usual.

The transmission curve:

♦ On the horizontal axis, the wavelength is plotted in nanometers. 400 nm corresponds to a deep blue, at 520 nm the human eye sees green, at 600 nm red.

At 656 nm is the known H-alpha emission line of hydrogen, around 500 nm the two [O III] lines of oxygen, at 486 nm the H-beta line of hydrogen, around 672 nm the two [S II] lines of sulfur. The square brackets indicate that these are forbidden lines.

♦ On the vertical axis the transmission is plotted in %.

♦ The cyan line shows the transmission of the filter.

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 R/RP full-frame 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