The UHC (Ultra High Contrast) astronomical filter is the filter dedicated to visual observation.

You will enjoy your UHC astronomical filter with which you will see more stars and more objects in the deep sky than with any other filter from other manufacturers.

The UHC astronomical filter allows almost 100% transmission of all radiation from the OIII and Hbeta lines. However, the second window of the Halpha line is not intended for visual observation. It is important to know if the filter is used with an electronic module. All other irrelevant scattered light from other wavelengths and partially containing artificial light pollution is effectively stopped by the filter. The strong blocking of radiation from the sky background brings an unexpected abundance of visible detail in gas nebulae and planetary nebulae.

This filter is a universal filter suitable for visual observation in areas polluted by artificial lighting. Even through small telescopes, it enhances the contrasts between emission nebulae and comets and, the deep sky. It is highly recommended for comet viewing!
In addition, the UHC filter increases the contrast of nebulous objects and faint stars. The resulting application range spans an aperture ratio of 1:3 to 1:15 for telescopes with apertures up to 5" (125mm). It allows observation of gas clouds and planetary nebulae in regions outside the city and also in regions affected by pollution from artificial light sources.

Operating mode

The filter completely blocks the emission lines of lighting from artificial sources such as low and high pressure lamps (mercury (Hg) and sodium (Na) lamps) and the lines of Airglow (luminescence phenomenon of the 'universe). As a result, there is an increase in the contrast between the deep sky and the observation objects, which is, because of the minimum value of the bandwidth at mid-peak height, however smaller than that obtained for the UHC filter. . The passband of the filter corresponds to an emission line which mainly occurs in the tails of comets.

UHC filters have a staggering light transmission rate, giving the observer much better deep sky views even through small telescopes!

The high transmittance of the filter's optical glass means that enough light is available to allow successful visual observation with telescopes having an aperture of 2" (50mm). The astronomical filters are perfected for use with telescopes with a focal length f/ratio between f/4 and f/15.

Transmission losses and chromatic distortion phenomena, which arise with other filters, only occur with astronomical filters when the very bright aperture ratios are greater than or equal to 1:2. Another huge advantage of your astronomical filter is the high optical quality of your glass filter.

Usage tips

•     perfect for observing comets outside the city with telescopes of any aperture
•     experimental for the observation of the clouds of Jupiter
•     better separation of double stars
•     As a Clip EOS filter, it enables photography with single-lens reflex cameras (DSLR) even under extreme light pollution conditions, without affecting the color balance.

Alternatives

UHC filters are recommended for telescopes with an aperture greater than or equal to 5" (125mm), which offer a strong contrast enhancement. From an aperture of 10" (250mm), the OIII filter can also be used, since the narrowness of its band increases the contrast remarkably for certain objects.

Filter compatibility

•     visual observation (landscape): neutral, the use of a UHC filter is preferable
•     visual observation (city): good, for telescopes of medium magnification and aperture up to 125mm
•     conventional film: good, however very long exposure times
•     CCD (Charge Coupled Device) astrophotography: good, additional IR blocker essential
•     DSLR (Digital Sensor Lens Reflex) astrophotography (unmodified): good, white color balance is very good
•     DSLR astrophotography (astro modified): good, the white color balance is very good
•     DSLR astrophotography (equipped with clear glass, multi-coated (MC)): good, additional IR blocker essential
•     Webcam / Video (planets): incompatible
•     Webcam / Video (Deep Sky): very good with the presence of artificial light pollution

Filter technical data

•     94% transmittance at 486nm (H-beta)
•     95% transmittance at 496nm (OIII)
•     95% transmittance at 501nm (OIII)
•     88% transmission at 656nm (H alpha)
•     maximum transmission at approx. 95%
•     bandwidth: from 465nm to 530nm and from 645nm and beyond
•     homofocal with all other astronomical filters
•     filter thickness: 1mm
•     not sensitive to moisture, not alterable, scratch resistant
•     support material polished using a very sophisticated optical method
•     The filter is delivered in a resistant packaging