| This 48mm filter threads into most 2” eyepieces, except those Meade Ultra Wide Angles and TeleVue Naglers which have dual (2” and 1.25”) barrels. These eyepieces must use 1.25” filters. This filter has an extra-wide extra-wide 900 Ångstrom visual passband designed for visually enhancing emission nebulas and the violet reflected starlight of reflection nebulas with all telescope types. It threads into Lumicon’s Giant Easy Guider, Cassegrain Easy Guider, and 2” Newtonian Easy Guider for astrophotography. It has peak transmission at the visually important emission lines of hydrogen-beta at 4861Å and doubly ionized oxygen at 4959Å and 5007Å. It also has high transmission at the photographically important ionized nitrogen and hydrogen-alpha lines near 6570Å. While its extra-wide passband makes it very good for reflection nebulas, it is somewhat less useful at severely light-polluted sites than a narrowband filter, since some blue-white mercury light pollution is allowed through. 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. Individually-measured transmission data is provided 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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