EXPLORE SCIENTIFIC 2" UHC Nebula Filter (Refurbished)

One of the most important obstacles for the exploration of the night sky is the brightening of the night sky by artificial lights, such as streetlights. The night sky is not really dark in the vicinity of towns or cities, which reduces the visibility of objects beyond the solar system enormously. Depending on the type of the celestial object, it is possible to dramatically increase the contrast by blocking annoying artificial light. The EXPLORE SCIENTIFIC UHC filter "zeros in" on the wavelengths of so-called emission nebulae. Those objects glow in special colours - their emission lines. Those emission lines are linked to chemical elements - in this case hydrogen at 486nm and 656nm, plus oxygen at 496nm and 501nm. The EXPLORE SCIENTIFIC UHC nebula filter blocks all other colour wavelengths (and thereby nearly all of artificial light) and only the emission line of the hydrogen and oxygen can pass the filter. The result is astonishing: suddenly nebulae are visible at locations that were completely invisible from, without filters. In suburban skies, for example the Owl-nebula M97, the Veil-nebula NGC 6992 or even the bright Dumbell-nebula M27 are not clearly visible. Using this filter allows you to see nebulae and their structures in much finer detail. A must for every visual observer. The Explore Scientific nebula filters come with a individual test certificate - your guarantee to receive a premium filter.