The Astronomik UHC (Ultra High Contrast) for Pentax K transmits nearly 100% of the radiation from both the OIII and H-beta lines. All annoying, scattered light from other wavelength sources--including local artificial light pollution--is reliably filtered out. Blocking out this light with such strength presents an unexpected wealth of detail in the night sky, especially for visible gas and planetary nebulae.
The astounding high light transmission of these UHC filters brings better views of deep-sky-objects even to smaller telescopes. With the high transmission of the optical glass filters, enough light is available for successful visual observations with telescopes beginning at 2" (50mm) aperture. The Astronomik filters are optimized for use with telescope focal length f-ratios of f/4 to f/15.Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when using an extremely fast aperture ratio of 1.2 or more.
The Astronomik UHC filters offer a transmission rate of 97% for H-beta (486nm), OIII (496nm), OIII (501nm), and H-alpha (656 nm). For optimal performance, these filters are best used with telescopes with focal ratios between f/3.5 and f/10. These are also both scratch-resistant and not sensitive to humidity or aging with their excellent craft materials. These filters will not reduce the optical performance of your telescope and are parfocal with other Astronomik filters
Another major advantage of the Astronomik UHC filter is the high optical quality of the filter glass. When using Astronomik UHC filters you will quickly notice the same needle-sharp stars which you are familiar with from your astronomical instrument without any filter!
- Visual Observing (Dark Skies): Very good for all telescopes and has a high exit pupil
- Visual Observation (Urban Skies): Very good for telescopes from 100 mm aperture and up
- CCD Photography: Good when used with an additional IR-block-filter
- DSLR Photography: Good. Color balance is slightly shifted but contrast is enhanced
- DSLR Photography (Astro Modified): Very good with near perfect color balance
- DSLR Photography (MC Modified): Good when used with an additional IR-block-filter
- Webcam / Video (Planets): Unsuitable
- Webcam / Video (Deep Sky): Good if light pollution is a big problem