If you have a Canon EOS DSLR Camera you can filter out a lot of light pollution by using a clip-in filter that "sits" in the recessed area just inside the body of the camera once your lens has been removed. This means that if you change lenses during an imaging session you do not need to remove the filter. The clip-in filter also acts like a dust cover for your sensor.
The City Light Suppression (CLS) filter from SkyTech is designed to improve the visibility of various deep sky objects by blocking light pollution, while letting through the light from the deep sky objects. Artificial street lighting such as mercury vapour lamps, both high & low pressure sodium vapour lights and unwanted natural light caused by neutral oxygen emission in our atmosphere (skyglow) are almost completely suppressed by the SkyTech CLS filter. The filter selectively allows light from deepsky objects through, with high transmission of ionised oxygen O-III (496nm & 500nm), Hydrogen Beta / N-beta (486nm), N-II(654nm and 658nm), H-alpha(656nm) and S-II(672nm). By selectively blocking light pollution and transmitting these desirable wavelengths, the contrast and detail of deepsky objects is greatly enhanced.
SkyTech CLS filters are suitable for unmodified Canon DSLRs. The CLS has a wider pass-band than a UHC filter, so it gives a more natural colour rendition than a UHC filter. The CLS filter is therefore best for mild to moderate light pollution on city outskirts or suburban locations. It is compatible with all APS-C sized Canon EOS cameras and not for full frame cameras. We note that these are not to be used with Canon EFS lenses because the rear elements are longer then EF lenses and thus can strike the filter. This is not an issue with most Sigma and 3rd party EF-S lenses and of course telescopes.
- The filter can be inserted and removed in seconds.
- All lens functions (focus, preview screen, image stabilization) work as usual.
- If you have a telescope with short space between reducer/flattener and camera and filter wheel, a clip filter is the solution.
- It protects your sensor from dust build-up during long exposures.
- Precision laser-cut housing.
- Schott glass substrate material with precision polish.
- Glass thickness 1.0 mm.
- Surface Quality: 60/40 (Refer to MIL-O-13830)
- Fine-optically polished to ensure accurate 1/4 wavefront and < 30 sec parallelism over both surfaces
- 95% transmission of main nebula emission lines (i.e. Ha 656nm, OIII 496nm & 500nm, SII 672nm and H-beta 486nm).
- 0.1% transmission of off-band, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm).
Dichroic Filter Coatings:
- Multi-layer anti-reflection coating (AR Coat).
- Special high homogeneity coating process with electron-beam gun evaporation and Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) no deviation with temperature change.
Note on availability: We can supply to the EU but these EOS Clip filters cannot be shipped to Germany.
Please note: We noticed certain models of Canon camera have a looser fit than others, causing the filter to rattle or rotate slightly. The EOS 70D is one such camera, having a wider aperture into which the filter must fit. Please see instructional image attached for adjusting your SkyTech filter for a tighter fit. This is the same procedure as for other clip filters.