Astronomik UHC-E deepsky filter (2")

The Astronomik UHC-E filter is our budget filter for deep-sky observation of emission nebulae and comets under light polluted skies. It’s particularly suitable for small ’scopes.

The UHC-E Filter increases contrast of emission nebulae and comets and blocks the light of typical streetlights as well as airglow. It is best suited for telescopes up to 5" / 125mm.

Main use

The Astronomik UHC-E filter provides a FWHM of 45nm and blocks the light of typical streetlights (e.g. sodium and mercury vapour) as well as airglow. Thus it increases contrast between your target and the night sky. The contrast enhancement is less than that of the Astronomik UHC filter, but at the same time the transmitted amount of starlight is greater. It's therefore better suited to smaller telescopes. As the UHC-E filter passes a spectral line of Carbon (due to the higher FWHM) it opens up the possibility of comet observation.

Other uses

• Observation of Jupiter’s clouds.
• Easier resolution of Double Stars.
• Photography under light-polluted skies with DSLRs and other cameras.

Alternatives

If you use a telescope with an aperture larger than 5", we suggest the use of our standard UHC-filter because of its greater contrast enhancement capabilities. If you use a telescope larger than 8", you can try our OIII filter for even better results when observing specific nebulae.

The UHC filters are general purpose deepsky filters which blocks the light from Hg and Na lamps, but transmits all of important wavelengths, such as H-alpha, H-beta and O-III. UHC filters are available from many different manufacturers, checking the image below might help to choose the right one. As it is evident there is no such thing as UHC "standard". All of the filters transmits most of the light around H-alpha (656nm), Oxigen-III (501nm) and H-beta (485) lines. 

There are wider and narrower filters. But what might be the difference between them in practice? It depends on heavily the selected targets.

A general rule is that the narrowed the transmission is the higher the contrast is, meaning that they work excellently for emission, planetary nebulae and supernova remnants. They don't work that well on objects with wider spectrum, like stellar clusters, galaxies, open- and globular clusters. To photograph these a wider transmission, light pollution reduction filters are recommended.

So: for emission and planetary nebulae, and supernova remnant use a narrowband filter, like Astronomik or Castell UHC.