Filter Astronomik UHC in the frame 1.25 "/ 31.7 mm.
Astronomer UHC filter is the right filter for visual observation. This is the filter. The UHC filter passes almost 100% of the radiation from the O-III and H-beta lines. If the filter will be used for shooting, it's good to know that it also lets in the H-alpha line. It is a very effective filter when you want to filter unwanted scattered light, including artificial light pollution. Thanks to the strong darkening of the background, it exposes the richness of detail of gas and planetary nebulae. The UHC Astronomic Filter improves the perception of deep sky objects (DSs) even with a small telescope - it can even be used with a 50 mm telescope (!). The filter is designed for telescopes with light intensity in the range f / 4 - f / 15. Losses on transmission, chromatic distortion can only occur with extremely bright lenses, f / 2 and lighter ones. The quality of the filter is so high that the images of the stars are point-like as if the filter was not used. • visual observations under the dark sky: very good, for all apertures, for large output pupils
• visual observations under the urban sky: very good, for telescopes with an aperture of min. 100 mm
• film photography: acceptable for very long exposure times
• CCD photography: good when used with an additional IR filter
• unmodified mirror photography: good, the color balance is shifted, but the contrast increases
• photo of a reflex camera modified for astrophotography: very good, the color balance is almost perfect
• webcam / video cameras for planetary photography: not applicable
• webcam / video cameras when photographing nebular objects: good if light pollution at the observation site is a big problem • completely blocks wavelengths that are an annoying background
• almost 100% of the routes of the O-III and H-beta lines
• transmission for H-alpha line is 96%
• Ideal versatile nebula filter even for small telescopes
• diffraction-limited accuracy
• parchocal with other Astronomic filters
• thickness: 1 mm
• resistant to moisture, scratch, does not age, without residual material stress 
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