The UHC Filter for Visual Use - T-thread Cell (M42 x 0.75) by Astronomik:
The Astronomik Ultra High Contrast filter is for visual deep-sky observation. It lets almost 100-percent of the radiation from both O-III lines and the H-beta line pass through. A second bandpass for the H-alpha line ensures that this radiation also reaches the eye, and scattered light from other wavelength ranges is also filtered out. Due to the strong reduction of the sky background, gas and planetary nebulas are visible with an unexpected abundance of detail. Because of the high transmission, the UHC filter provides enough light to successfully observe deep-sky objects with smaller telescopes.
The filters are optimized for use with focal ratios of f/4 to f/15. Unlike other filters on the market, loss of transmission and color displacement with the Astronomik filter occurs only on telescopes with extremely fast focal ratios of f/3 on up. Compared to the UHC filters sold by other manufacturers, the Astronomik UHC filter shows you more stars and more details in nebulas, and because of the high quality of the glass, you will see stars as small pinpoints.
Astronomik filters are in a class by themselves when compared to other filters made by Japanese and US manufacturers. The coatings are completely sealed and insensitive to moisture. They do not change with the years, but keep their transmission characteristics indefinitely. The coatings are so hard that is it not possible to scratch them by mistake. You would have to rub them with sandpaper to get even the finest of scratches! Due to these outstanding characteristics, Astronomik gives them a 5 year guarantee. Each filter will be sent in a useful protective case.
Astronomik UHC Filter for Visual Use Features:
- Transmission of nearly 100-percent of O-III and H-beta
- Transmission of 96-percent of H-alpha
- Entire Blocking of annoying wavelengths
- Ideal All-round Deep Sky filter even for small telescopes
- Not sensitive to humidity or aging
- Excellent carrier material. The optical performance of your telescope is not reduced by the filter in any way.
- Parfocal with other Astronomik filters
- Glass thickness: 1mm
- Completely resistant against high humidity, scratches and aging effects
- Diffraction limited, the filter will not reduce the optical performance of your telescope!
- Astronomik filters are delivered in a high-quality, long lasting, filter box
OPT Product Number: AK-UHC-T