| Unlike stars, emission nebulas give off light in a very narrow range of wavelengths. This 2" Orion SkyGlow contrast-enhancing filter allows maximum transmission of the light that is most commonly emitted by nebulas, while blocking the unwanted glare of city lights and the natural sky glow of ionized gasses in our atmosphere. The SkyGlow filter’s wide 650 Ångstrom visual passband enhances the appearance of emission nebulas and the violet reflected starlight of reflection nebulas with all telescope types. It is also useful photographically with 1.25" camera adapters. Its advanced multilayer ion-deposited “interference" design has peak transmission in the 95% or greater range at the visually important emission lines of hydrogen-beta at 4861Å and doubly ionized oxygen at 4959Å and 5007Å. It also has a similarly high transmission at the photographically important (but visually imperceptible) ionized nitrogen and hydrogen-alpha lines near 6570Å. Its wide passband makes it good for showing the reflected starlight of reflection nebulas from dark sky and suburban sites. However, it is somewhat less useful for this purpose at severely light-polluted sites. Its wide passband allows some blue-white mercury light pollution through, which can reduce the contrast of reflection nebula details. Brighter nebulas such as the Dumbbell, Omega, and Lagoon stand out well at suburban sites; faint nebulas such as the Veil, North America, and Pelican are not only visible from suburban sites, but have more detail and higher contrast from dark sky sites. Views of galaxies and star clusters are also enhanced, although not as much as nebulas. The filter comes in a protective hard plastic case. An individually-measured light transmission curve is supplied with each filter. Enter your telescope focal ratio in the formula box to the right to see what focal length eyepieces will work best with this filter.
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